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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 18:49:45 +0000
commit2c3c1048746a4622d8c89a29670120dc8fab93c4 (patch)
tree848558de17fb3008cdf4d861b01ac7781903ce39 /arch/arm64/kernel/fpsimd.c
parentInitial commit. (diff)
downloadlinux-2c3c1048746a4622d8c89a29670120dc8fab93c4.tar.xz
linux-2c3c1048746a4622d8c89a29670120dc8fab93c4.zip
Adding upstream version 6.1.76.upstream/6.1.76
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'arch/arm64/kernel/fpsimd.c')
-rw-r--r--arch/arm64/kernel/fpsimd.c2059
1 files changed, 2059 insertions, 0 deletions
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
new file mode 100644
index 000000000..8c226d79a
--- /dev/null
+++ b/arch/arm64/kernel/fpsimd.c
@@ -0,0 +1,2059 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * FP/SIMD context switching and fault handling
+ *
+ * Copyright (C) 2012 ARM Ltd.
+ * Author: Catalin Marinas <catalin.marinas@arm.com>
+ */
+
+#include <linux/bitmap.h>
+#include <linux/bitops.h>
+#include <linux/bottom_half.h>
+#include <linux/bug.h>
+#include <linux/cache.h>
+#include <linux/compat.h>
+#include <linux/compiler.h>
+#include <linux/cpu.h>
+#include <linux/cpu_pm.h>
+#include <linux/ctype.h>
+#include <linux/kernel.h>
+#include <linux/linkage.h>
+#include <linux/irqflags.h>
+#include <linux/init.h>
+#include <linux/percpu.h>
+#include <linux/prctl.h>
+#include <linux/preempt.h>
+#include <linux/ptrace.h>
+#include <linux/sched/signal.h>
+#include <linux/sched/task_stack.h>
+#include <linux/signal.h>
+#include <linux/slab.h>
+#include <linux/stddef.h>
+#include <linux/sysctl.h>
+#include <linux/swab.h>
+
+#include <asm/esr.h>
+#include <asm/exception.h>
+#include <asm/fpsimd.h>
+#include <asm/cpufeature.h>
+#include <asm/cputype.h>
+#include <asm/neon.h>
+#include <asm/processor.h>
+#include <asm/simd.h>
+#include <asm/sigcontext.h>
+#include <asm/sysreg.h>
+#include <asm/traps.h>
+#include <asm/virt.h>
+
+#define FPEXC_IOF (1 << 0)
+#define FPEXC_DZF (1 << 1)
+#define FPEXC_OFF (1 << 2)
+#define FPEXC_UFF (1 << 3)
+#define FPEXC_IXF (1 << 4)
+#define FPEXC_IDF (1 << 7)
+
+/*
+ * (Note: in this discussion, statements about FPSIMD apply equally to SVE.)
+ *
+ * In order to reduce the number of times the FPSIMD state is needlessly saved
+ * and restored, we need to keep track of two things:
+ * (a) for each task, we need to remember which CPU was the last one to have
+ * the task's FPSIMD state loaded into its FPSIMD registers;
+ * (b) for each CPU, we need to remember which task's userland FPSIMD state has
+ * been loaded into its FPSIMD registers most recently, or whether it has
+ * been used to perform kernel mode NEON in the meantime.
+ *
+ * For (a), we add a fpsimd_cpu field to thread_struct, which gets updated to
+ * the id of the current CPU every time the state is loaded onto a CPU. For (b),
+ * we add the per-cpu variable 'fpsimd_last_state' (below), which contains the
+ * address of the userland FPSIMD state of the task that was loaded onto the CPU
+ * the most recently, or NULL if kernel mode NEON has been performed after that.
+ *
+ * With this in place, we no longer have to restore the next FPSIMD state right
+ * when switching between tasks. Instead, we can defer this check to userland
+ * resume, at which time we verify whether the CPU's fpsimd_last_state and the
+ * task's fpsimd_cpu are still mutually in sync. If this is the case, we
+ * can omit the FPSIMD restore.
+ *
+ * As an optimization, we use the thread_info flag TIF_FOREIGN_FPSTATE to
+ * indicate whether or not the userland FPSIMD state of the current task is
+ * present in the registers. The flag is set unless the FPSIMD registers of this
+ * CPU currently contain the most recent userland FPSIMD state of the current
+ * task. If the task is behaving as a VMM, then this is will be managed by
+ * KVM which will clear it to indicate that the vcpu FPSIMD state is currently
+ * loaded on the CPU, allowing the state to be saved if a FPSIMD-aware
+ * softirq kicks in. Upon vcpu_put(), KVM will save the vcpu FP state and
+ * flag the register state as invalid.
+ *
+ * In order to allow softirq handlers to use FPSIMD, kernel_neon_begin() may
+ * save the task's FPSIMD context back to task_struct from softirq context.
+ * To prevent this from racing with the manipulation of the task's FPSIMD state
+ * from task context and thereby corrupting the state, it is necessary to
+ * protect any manipulation of a task's fpsimd_state or TIF_FOREIGN_FPSTATE
+ * flag with {, __}get_cpu_fpsimd_context(). This will still allow softirqs to
+ * run but prevent them to use FPSIMD.
+ *
+ * For a certain task, the sequence may look something like this:
+ * - the task gets scheduled in; if both the task's fpsimd_cpu field
+ * contains the id of the current CPU, and the CPU's fpsimd_last_state per-cpu
+ * variable points to the task's fpsimd_state, the TIF_FOREIGN_FPSTATE flag is
+ * cleared, otherwise it is set;
+ *
+ * - the task returns to userland; if TIF_FOREIGN_FPSTATE is set, the task's
+ * userland FPSIMD state is copied from memory to the registers, the task's
+ * fpsimd_cpu field is set to the id of the current CPU, the current
+ * CPU's fpsimd_last_state pointer is set to this task's fpsimd_state and the
+ * TIF_FOREIGN_FPSTATE flag is cleared;
+ *
+ * - the task executes an ordinary syscall; upon return to userland, the
+ * TIF_FOREIGN_FPSTATE flag will still be cleared, so no FPSIMD state is
+ * restored;
+ *
+ * - the task executes a syscall which executes some NEON instructions; this is
+ * preceded by a call to kernel_neon_begin(), which copies the task's FPSIMD
+ * register contents to memory, clears the fpsimd_last_state per-cpu variable
+ * and sets the TIF_FOREIGN_FPSTATE flag;
+ *
+ * - the task gets preempted after kernel_neon_end() is called; as we have not
+ * returned from the 2nd syscall yet, TIF_FOREIGN_FPSTATE is still set so
+ * whatever is in the FPSIMD registers is not saved to memory, but discarded.
+ */
+struct fpsimd_last_state_struct {
+ struct user_fpsimd_state *st;
+ void *sve_state;
+ void *za_state;
+ u64 *svcr;
+ unsigned int sve_vl;
+ unsigned int sme_vl;
+};
+
+static DEFINE_PER_CPU(struct fpsimd_last_state_struct, fpsimd_last_state);
+
+__ro_after_init struct vl_info vl_info[ARM64_VEC_MAX] = {
+#ifdef CONFIG_ARM64_SVE
+ [ARM64_VEC_SVE] = {
+ .type = ARM64_VEC_SVE,
+ .name = "SVE",
+ .min_vl = SVE_VL_MIN,
+ .max_vl = SVE_VL_MIN,
+ .max_virtualisable_vl = SVE_VL_MIN,
+ },
+#endif
+#ifdef CONFIG_ARM64_SME
+ [ARM64_VEC_SME] = {
+ .type = ARM64_VEC_SME,
+ .name = "SME",
+ },
+#endif
+};
+
+static unsigned int vec_vl_inherit_flag(enum vec_type type)
+{
+ switch (type) {
+ case ARM64_VEC_SVE:
+ return TIF_SVE_VL_INHERIT;
+ case ARM64_VEC_SME:
+ return TIF_SME_VL_INHERIT;
+ default:
+ WARN_ON_ONCE(1);
+ return 0;
+ }
+}
+
+struct vl_config {
+ int __default_vl; /* Default VL for tasks */
+};
+
+static struct vl_config vl_config[ARM64_VEC_MAX];
+
+static inline int get_default_vl(enum vec_type type)
+{
+ return READ_ONCE(vl_config[type].__default_vl);
+}
+
+#ifdef CONFIG_ARM64_SVE
+
+static inline int get_sve_default_vl(void)
+{
+ return get_default_vl(ARM64_VEC_SVE);
+}
+
+static inline void set_default_vl(enum vec_type type, int val)
+{
+ WRITE_ONCE(vl_config[type].__default_vl, val);
+}
+
+static inline void set_sve_default_vl(int val)
+{
+ set_default_vl(ARM64_VEC_SVE, val);
+}
+
+static void __percpu *efi_sve_state;
+
+#else /* ! CONFIG_ARM64_SVE */
+
+/* Dummy declaration for code that will be optimised out: */
+extern void __percpu *efi_sve_state;
+
+#endif /* ! CONFIG_ARM64_SVE */
+
+#ifdef CONFIG_ARM64_SME
+
+static int get_sme_default_vl(void)
+{
+ return get_default_vl(ARM64_VEC_SME);
+}
+
+static void set_sme_default_vl(int val)
+{
+ set_default_vl(ARM64_VEC_SME, val);
+}
+
+static void sme_free(struct task_struct *);
+
+#else
+
+static inline void sme_free(struct task_struct *t) { }
+
+#endif
+
+DEFINE_PER_CPU(bool, fpsimd_context_busy);
+EXPORT_PER_CPU_SYMBOL(fpsimd_context_busy);
+
+static void fpsimd_bind_task_to_cpu(void);
+
+static void __get_cpu_fpsimd_context(void)
+{
+ bool busy = __this_cpu_xchg(fpsimd_context_busy, true);
+
+ WARN_ON(busy);
+}
+
+/*
+ * Claim ownership of the CPU FPSIMD context for use by the calling context.
+ *
+ * The caller may freely manipulate the FPSIMD context metadata until
+ * put_cpu_fpsimd_context() is called.
+ *
+ * The double-underscore version must only be called if you know the task
+ * can't be preempted.
+ *
+ * On RT kernels local_bh_disable() is not sufficient because it only
+ * serializes soft interrupt related sections via a local lock, but stays
+ * preemptible. Disabling preemption is the right choice here as bottom
+ * half processing is always in thread context on RT kernels so it
+ * implicitly prevents bottom half processing as well.
+ */
+static void get_cpu_fpsimd_context(void)
+{
+ if (!IS_ENABLED(CONFIG_PREEMPT_RT))
+ local_bh_disable();
+ else
+ preempt_disable();
+ __get_cpu_fpsimd_context();
+}
+
+static void __put_cpu_fpsimd_context(void)
+{
+ bool busy = __this_cpu_xchg(fpsimd_context_busy, false);
+
+ WARN_ON(!busy); /* No matching get_cpu_fpsimd_context()? */
+}
+
+/*
+ * Release the CPU FPSIMD context.
+ *
+ * Must be called from a context in which get_cpu_fpsimd_context() was
+ * previously called, with no call to put_cpu_fpsimd_context() in the
+ * meantime.
+ */
+static void put_cpu_fpsimd_context(void)
+{
+ __put_cpu_fpsimd_context();
+ if (!IS_ENABLED(CONFIG_PREEMPT_RT))
+ local_bh_enable();
+ else
+ preempt_enable();
+}
+
+static bool have_cpu_fpsimd_context(void)
+{
+ return !preemptible() && __this_cpu_read(fpsimd_context_busy);
+}
+
+unsigned int task_get_vl(const struct task_struct *task, enum vec_type type)
+{
+ return task->thread.vl[type];
+}
+
+void task_set_vl(struct task_struct *task, enum vec_type type,
+ unsigned long vl)
+{
+ task->thread.vl[type] = vl;
+}
+
+unsigned int task_get_vl_onexec(const struct task_struct *task,
+ enum vec_type type)
+{
+ return task->thread.vl_onexec[type];
+}
+
+void task_set_vl_onexec(struct task_struct *task, enum vec_type type,
+ unsigned long vl)
+{
+ task->thread.vl_onexec[type] = vl;
+}
+
+/*
+ * TIF_SME controls whether a task can use SME without trapping while
+ * in userspace, when TIF_SME is set then we must have storage
+ * alocated in sve_state and za_state to store the contents of both ZA
+ * and the SVE registers for both streaming and non-streaming modes.
+ *
+ * If both SVCR.ZA and SVCR.SM are disabled then at any point we
+ * may disable TIF_SME and reenable traps.
+ */
+
+
+/*
+ * TIF_SVE controls whether a task can use SVE without trapping while
+ * in userspace, and also (together with TIF_SME) the way a task's
+ * FPSIMD/SVE state is stored in thread_struct.
+ *
+ * The kernel uses this flag to track whether a user task is actively
+ * using SVE, and therefore whether full SVE register state needs to
+ * be tracked. If not, the cheaper FPSIMD context handling code can
+ * be used instead of the more costly SVE equivalents.
+ *
+ * * TIF_SVE or SVCR.SM set:
+ *
+ * The task can execute SVE instructions while in userspace without
+ * trapping to the kernel.
+ *
+ * When stored, Z0-Z31 (incorporating Vn in bits[127:0] or the
+ * corresponding Zn), P0-P15 and FFR are encoded in
+ * task->thread.sve_state, formatted appropriately for vector
+ * length task->thread.sve_vl or, if SVCR.SM is set,
+ * task->thread.sme_vl.
+ *
+ * task->thread.sve_state must point to a valid buffer at least
+ * sve_state_size(task) bytes in size.
+ *
+ * During any syscall, the kernel may optionally clear TIF_SVE and
+ * discard the vector state except for the FPSIMD subset.
+ *
+ * * TIF_SVE clear:
+ *
+ * An attempt by the user task to execute an SVE instruction causes
+ * do_sve_acc() to be called, which does some preparation and then
+ * sets TIF_SVE.
+ *
+ * When stored, FPSIMD registers V0-V31 are encoded in
+ * task->thread.uw.fpsimd_state; bits [max : 128] for each of Z0-Z31 are
+ * logically zero but not stored anywhere; P0-P15 and FFR are not
+ * stored and have unspecified values from userspace's point of
+ * view. For hygiene purposes, the kernel zeroes them on next use,
+ * but userspace is discouraged from relying on this.
+ *
+ * task->thread.sve_state does not need to be non-NULL, valid or any
+ * particular size: it must not be dereferenced.
+ *
+ * * FPSR and FPCR are always stored in task->thread.uw.fpsimd_state
+ * irrespective of whether TIF_SVE is clear or set, since these are
+ * not vector length dependent.
+ */
+
+/*
+ * Update current's FPSIMD/SVE registers from thread_struct.
+ *
+ * This function should be called only when the FPSIMD/SVE state in
+ * thread_struct is known to be up to date, when preparing to enter
+ * userspace.
+ */
+static void task_fpsimd_load(void)
+{
+ bool restore_sve_regs = false;
+ bool restore_ffr;
+
+ WARN_ON(!system_supports_fpsimd());
+ WARN_ON(!have_cpu_fpsimd_context());
+
+ /* Check if we should restore SVE first */
+ if (IS_ENABLED(CONFIG_ARM64_SVE) && test_thread_flag(TIF_SVE)) {
+ sve_set_vq(sve_vq_from_vl(task_get_sve_vl(current)) - 1);
+ restore_sve_regs = true;
+ restore_ffr = true;
+ }
+
+ /* Restore SME, override SVE register configuration if needed */
+ if (system_supports_sme()) {
+ unsigned long sme_vl = task_get_sme_vl(current);
+
+ /* Ensure VL is set up for restoring data */
+ if (test_thread_flag(TIF_SME))
+ sme_set_vq(sve_vq_from_vl(sme_vl) - 1);
+
+ write_sysreg_s(current->thread.svcr, SYS_SVCR);
+
+ if (thread_za_enabled(&current->thread))
+ za_load_state(current->thread.za_state);
+
+ if (thread_sm_enabled(&current->thread)) {
+ restore_sve_regs = true;
+ restore_ffr = system_supports_fa64();
+ }
+ }
+
+ if (restore_sve_regs)
+ sve_load_state(sve_pffr(&current->thread),
+ &current->thread.uw.fpsimd_state.fpsr,
+ restore_ffr);
+ else
+ fpsimd_load_state(&current->thread.uw.fpsimd_state);
+}
+
+/*
+ * Ensure FPSIMD/SVE storage in memory for the loaded context is up to
+ * date with respect to the CPU registers. Note carefully that the
+ * current context is the context last bound to the CPU stored in
+ * last, if KVM is involved this may be the guest VM context rather
+ * than the host thread for the VM pointed to by current. This means
+ * that we must always reference the state storage via last rather
+ * than via current, other than the TIF_ flags which KVM will
+ * carefully maintain for us.
+ */
+static void fpsimd_save(void)
+{
+ struct fpsimd_last_state_struct const *last =
+ this_cpu_ptr(&fpsimd_last_state);
+ /* set by fpsimd_bind_task_to_cpu() or fpsimd_bind_state_to_cpu() */
+ bool save_sve_regs = false;
+ bool save_ffr;
+ unsigned int vl;
+
+ WARN_ON(!system_supports_fpsimd());
+ WARN_ON(!have_cpu_fpsimd_context());
+
+ if (test_thread_flag(TIF_FOREIGN_FPSTATE))
+ return;
+
+ if (test_thread_flag(TIF_SVE)) {
+ save_sve_regs = true;
+ save_ffr = true;
+ vl = last->sve_vl;
+ }
+
+ if (system_supports_sme()) {
+ u64 *svcr = last->svcr;
+
+ *svcr = read_sysreg_s(SYS_SVCR);
+
+ if (*svcr & SVCR_ZA_MASK)
+ za_save_state(last->za_state);
+
+ /* If we are in streaming mode override regular SVE. */
+ if (*svcr & SVCR_SM_MASK) {
+ save_sve_regs = true;
+ save_ffr = system_supports_fa64();
+ vl = last->sme_vl;
+ }
+ }
+
+ if (IS_ENABLED(CONFIG_ARM64_SVE) && save_sve_regs) {
+ /* Get the configured VL from RDVL, will account for SM */
+ if (WARN_ON(sve_get_vl() != vl)) {
+ /*
+ * Can't save the user regs, so current would
+ * re-enter user with corrupt state.
+ * There's no way to recover, so kill it:
+ */
+ force_signal_inject(SIGKILL, SI_KERNEL, 0, 0);
+ return;
+ }
+
+ sve_save_state((char *)last->sve_state +
+ sve_ffr_offset(vl),
+ &last->st->fpsr, save_ffr);
+ } else {
+ fpsimd_save_state(last->st);
+ }
+}
+
+/*
+ * All vector length selection from userspace comes through here.
+ * We're on a slow path, so some sanity-checks are included.
+ * If things go wrong there's a bug somewhere, but try to fall back to a
+ * safe choice.
+ */
+static unsigned int find_supported_vector_length(enum vec_type type,
+ unsigned int vl)
+{
+ struct vl_info *info = &vl_info[type];
+ int bit;
+ int max_vl = info->max_vl;
+
+ if (WARN_ON(!sve_vl_valid(vl)))
+ vl = info->min_vl;
+
+ if (WARN_ON(!sve_vl_valid(max_vl)))
+ max_vl = info->min_vl;
+
+ if (vl > max_vl)
+ vl = max_vl;
+ if (vl < info->min_vl)
+ vl = info->min_vl;
+
+ bit = find_next_bit(info->vq_map, SVE_VQ_MAX,
+ __vq_to_bit(sve_vq_from_vl(vl)));
+ return sve_vl_from_vq(__bit_to_vq(bit));
+}
+
+#if defined(CONFIG_ARM64_SVE) && defined(CONFIG_SYSCTL)
+
+static int vec_proc_do_default_vl(struct ctl_table *table, int write,
+ void *buffer, size_t *lenp, loff_t *ppos)
+{
+ struct vl_info *info = table->extra1;
+ enum vec_type type = info->type;
+ int ret;
+ int vl = get_default_vl(type);
+ struct ctl_table tmp_table = {
+ .data = &vl,
+ .maxlen = sizeof(vl),
+ };
+
+ ret = proc_dointvec(&tmp_table, write, buffer, lenp, ppos);
+ if (ret || !write)
+ return ret;
+
+ /* Writing -1 has the special meaning "set to max": */
+ if (vl == -1)
+ vl = info->max_vl;
+
+ if (!sve_vl_valid(vl))
+ return -EINVAL;
+
+ set_default_vl(type, find_supported_vector_length(type, vl));
+ return 0;
+}
+
+static struct ctl_table sve_default_vl_table[] = {
+ {
+ .procname = "sve_default_vector_length",
+ .mode = 0644,
+ .proc_handler = vec_proc_do_default_vl,
+ .extra1 = &vl_info[ARM64_VEC_SVE],
+ },
+ { }
+};
+
+static int __init sve_sysctl_init(void)
+{
+ if (system_supports_sve())
+ if (!register_sysctl("abi", sve_default_vl_table))
+ return -EINVAL;
+
+ return 0;
+}
+
+#else /* ! (CONFIG_ARM64_SVE && CONFIG_SYSCTL) */
+static int __init sve_sysctl_init(void) { return 0; }
+#endif /* ! (CONFIG_ARM64_SVE && CONFIG_SYSCTL) */
+
+#if defined(CONFIG_ARM64_SME) && defined(CONFIG_SYSCTL)
+static struct ctl_table sme_default_vl_table[] = {
+ {
+ .procname = "sme_default_vector_length",
+ .mode = 0644,
+ .proc_handler = vec_proc_do_default_vl,
+ .extra1 = &vl_info[ARM64_VEC_SME],
+ },
+ { }
+};
+
+static int __init sme_sysctl_init(void)
+{
+ if (system_supports_sme())
+ if (!register_sysctl("abi", sme_default_vl_table))
+ return -EINVAL;
+
+ return 0;
+}
+
+#else /* ! (CONFIG_ARM64_SME && CONFIG_SYSCTL) */
+static int __init sme_sysctl_init(void) { return 0; }
+#endif /* ! (CONFIG_ARM64_SME && CONFIG_SYSCTL) */
+
+#define ZREG(sve_state, vq, n) ((char *)(sve_state) + \
+ (SVE_SIG_ZREG_OFFSET(vq, n) - SVE_SIG_REGS_OFFSET))
+
+#ifdef CONFIG_CPU_BIG_ENDIAN
+static __uint128_t arm64_cpu_to_le128(__uint128_t x)
+{
+ u64 a = swab64(x);
+ u64 b = swab64(x >> 64);
+
+ return ((__uint128_t)a << 64) | b;
+}
+#else
+static __uint128_t arm64_cpu_to_le128(__uint128_t x)
+{
+ return x;
+}
+#endif
+
+#define arm64_le128_to_cpu(x) arm64_cpu_to_le128(x)
+
+static void __fpsimd_to_sve(void *sst, struct user_fpsimd_state const *fst,
+ unsigned int vq)
+{
+ unsigned int i;
+ __uint128_t *p;
+
+ for (i = 0; i < SVE_NUM_ZREGS; ++i) {
+ p = (__uint128_t *)ZREG(sst, vq, i);
+ *p = arm64_cpu_to_le128(fst->vregs[i]);
+ }
+}
+
+/*
+ * Transfer the FPSIMD state in task->thread.uw.fpsimd_state to
+ * task->thread.sve_state.
+ *
+ * Task can be a non-runnable task, or current. In the latter case,
+ * the caller must have ownership of the cpu FPSIMD context before calling
+ * this function.
+ * task->thread.sve_state must point to at least sve_state_size(task)
+ * bytes of allocated kernel memory.
+ * task->thread.uw.fpsimd_state must be up to date before calling this
+ * function.
+ */
+static void fpsimd_to_sve(struct task_struct *task)
+{
+ unsigned int vq;
+ void *sst = task->thread.sve_state;
+ struct user_fpsimd_state const *fst = &task->thread.uw.fpsimd_state;
+
+ if (!system_supports_sve() && !system_supports_sme())
+ return;
+
+ vq = sve_vq_from_vl(thread_get_cur_vl(&task->thread));
+ __fpsimd_to_sve(sst, fst, vq);
+}
+
+/*
+ * Transfer the SVE state in task->thread.sve_state to
+ * task->thread.uw.fpsimd_state.
+ *
+ * Task can be a non-runnable task, or current. In the latter case,
+ * the caller must have ownership of the cpu FPSIMD context before calling
+ * this function.
+ * task->thread.sve_state must point to at least sve_state_size(task)
+ * bytes of allocated kernel memory.
+ * task->thread.sve_state must be up to date before calling this function.
+ */
+static void sve_to_fpsimd(struct task_struct *task)
+{
+ unsigned int vq, vl;
+ void const *sst = task->thread.sve_state;
+ struct user_fpsimd_state *fst = &task->thread.uw.fpsimd_state;
+ unsigned int i;
+ __uint128_t const *p;
+
+ if (!system_supports_sve() && !system_supports_sme())
+ return;
+
+ vl = thread_get_cur_vl(&task->thread);
+ vq = sve_vq_from_vl(vl);
+ for (i = 0; i < SVE_NUM_ZREGS; ++i) {
+ p = (__uint128_t const *)ZREG(sst, vq, i);
+ fst->vregs[i] = arm64_le128_to_cpu(*p);
+ }
+}
+
+#ifdef CONFIG_ARM64_SVE
+/*
+ * Call __sve_free() directly only if you know task can't be scheduled
+ * or preempted.
+ */
+static void __sve_free(struct task_struct *task)
+{
+ kfree(task->thread.sve_state);
+ task->thread.sve_state = NULL;
+}
+
+static void sve_free(struct task_struct *task)
+{
+ WARN_ON(test_tsk_thread_flag(task, TIF_SVE));
+
+ __sve_free(task);
+}
+
+/*
+ * Return how many bytes of memory are required to store the full SVE
+ * state for task, given task's currently configured vector length.
+ */
+size_t sve_state_size(struct task_struct const *task)
+{
+ unsigned int vl = 0;
+
+ if (system_supports_sve())
+ vl = task_get_sve_vl(task);
+ if (system_supports_sme())
+ vl = max(vl, task_get_sme_vl(task));
+
+ return SVE_SIG_REGS_SIZE(sve_vq_from_vl(vl));
+}
+
+/*
+ * Ensure that task->thread.sve_state is allocated and sufficiently large.
+ *
+ * This function should be used only in preparation for replacing
+ * task->thread.sve_state with new data. The memory is always zeroed
+ * here to prevent stale data from showing through: this is done in
+ * the interest of testability and predictability: except in the
+ * do_sve_acc() case, there is no ABI requirement to hide stale data
+ * written previously be task.
+ */
+void sve_alloc(struct task_struct *task, bool flush)
+{
+ if (task->thread.sve_state) {
+ if (flush)
+ memset(task->thread.sve_state, 0,
+ sve_state_size(task));
+ return;
+ }
+
+ /* This is a small allocation (maximum ~8KB) and Should Not Fail. */
+ task->thread.sve_state =
+ kzalloc(sve_state_size(task), GFP_KERNEL);
+}
+
+
+/*
+ * Force the FPSIMD state shared with SVE to be updated in the SVE state
+ * even if the SVE state is the current active state.
+ *
+ * This should only be called by ptrace. task must be non-runnable.
+ * task->thread.sve_state must point to at least sve_state_size(task)
+ * bytes of allocated kernel memory.
+ */
+void fpsimd_force_sync_to_sve(struct task_struct *task)
+{
+ fpsimd_to_sve(task);
+}
+
+/*
+ * Ensure that task->thread.sve_state is up to date with respect to
+ * the user task, irrespective of when SVE is in use or not.
+ *
+ * This should only be called by ptrace. task must be non-runnable.
+ * task->thread.sve_state must point to at least sve_state_size(task)
+ * bytes of allocated kernel memory.
+ */
+void fpsimd_sync_to_sve(struct task_struct *task)
+{
+ if (!test_tsk_thread_flag(task, TIF_SVE) &&
+ !thread_sm_enabled(&task->thread))
+ fpsimd_to_sve(task);
+}
+
+/*
+ * Ensure that task->thread.uw.fpsimd_state is up to date with respect to
+ * the user task, irrespective of whether SVE is in use or not.
+ *
+ * This should only be called by ptrace. task must be non-runnable.
+ * task->thread.sve_state must point to at least sve_state_size(task)
+ * bytes of allocated kernel memory.
+ */
+void sve_sync_to_fpsimd(struct task_struct *task)
+{
+ if (test_tsk_thread_flag(task, TIF_SVE) ||
+ thread_sm_enabled(&task->thread))
+ sve_to_fpsimd(task);
+}
+
+/*
+ * Ensure that task->thread.sve_state is up to date with respect to
+ * the task->thread.uw.fpsimd_state.
+ *
+ * This should only be called by ptrace to merge new FPSIMD register
+ * values into a task for which SVE is currently active.
+ * task must be non-runnable.
+ * task->thread.sve_state must point to at least sve_state_size(task)
+ * bytes of allocated kernel memory.
+ * task->thread.uw.fpsimd_state must already have been initialised with
+ * the new FPSIMD register values to be merged in.
+ */
+void sve_sync_from_fpsimd_zeropad(struct task_struct *task)
+{
+ unsigned int vq;
+ void *sst = task->thread.sve_state;
+ struct user_fpsimd_state const *fst = &task->thread.uw.fpsimd_state;
+
+ if (!test_tsk_thread_flag(task, TIF_SVE) &&
+ !thread_sm_enabled(&task->thread))
+ return;
+
+ vq = sve_vq_from_vl(thread_get_cur_vl(&task->thread));
+
+ memset(sst, 0, SVE_SIG_REGS_SIZE(vq));
+ __fpsimd_to_sve(sst, fst, vq);
+}
+
+int vec_set_vector_length(struct task_struct *task, enum vec_type type,
+ unsigned long vl, unsigned long flags)
+{
+ bool free_sme = false;
+
+ if (flags & ~(unsigned long)(PR_SVE_VL_INHERIT |
+ PR_SVE_SET_VL_ONEXEC))
+ return -EINVAL;
+
+ if (!sve_vl_valid(vl))
+ return -EINVAL;
+
+ /*
+ * Clamp to the maximum vector length that VL-agnostic code
+ * can work with. A flag may be assigned in the future to
+ * allow setting of larger vector lengths without confusing
+ * older software.
+ */
+ if (vl > VL_ARCH_MAX)
+ vl = VL_ARCH_MAX;
+
+ vl = find_supported_vector_length(type, vl);
+
+ if (flags & (PR_SVE_VL_INHERIT |
+ PR_SVE_SET_VL_ONEXEC))
+ task_set_vl_onexec(task, type, vl);
+ else
+ /* Reset VL to system default on next exec: */
+ task_set_vl_onexec(task, type, 0);
+
+ /* Only actually set the VL if not deferred: */
+ if (flags & PR_SVE_SET_VL_ONEXEC)
+ goto out;
+
+ if (vl == task_get_vl(task, type))
+ goto out;
+
+ /*
+ * To ensure the FPSIMD bits of the SVE vector registers are preserved,
+ * write any live register state back to task_struct, and convert to a
+ * regular FPSIMD thread.
+ */
+ if (task == current) {
+ get_cpu_fpsimd_context();
+
+ fpsimd_save();
+ }
+
+ fpsimd_flush_task_state(task);
+ if (test_and_clear_tsk_thread_flag(task, TIF_SVE) ||
+ thread_sm_enabled(&task->thread))
+ sve_to_fpsimd(task);
+
+ if (system_supports_sme()) {
+ if (type == ARM64_VEC_SME ||
+ !(task->thread.svcr & (SVCR_SM_MASK | SVCR_ZA_MASK))) {
+ /*
+ * We are changing the SME VL or weren't using
+ * SME anyway, discard the state and force a
+ * reallocation.
+ */
+ task->thread.svcr &= ~(SVCR_SM_MASK |
+ SVCR_ZA_MASK);
+ clear_tsk_thread_flag(task, TIF_SME);
+ free_sme = true;
+ }
+ }
+
+ if (task == current)
+ put_cpu_fpsimd_context();
+
+ task_set_vl(task, type, vl);
+
+ /*
+ * Free the changed states if they are not in use, SME will be
+ * reallocated to the correct size on next use and we just
+ * allocate SVE now in case it is needed for use in streaming
+ * mode.
+ */
+ if (system_supports_sve()) {
+ sve_free(task);
+ sve_alloc(task, true);
+ }
+
+ if (free_sme)
+ sme_free(task);
+
+out:
+ update_tsk_thread_flag(task, vec_vl_inherit_flag(type),
+ flags & PR_SVE_VL_INHERIT);
+
+ return 0;
+}
+
+/*
+ * Encode the current vector length and flags for return.
+ * This is only required for prctl(): ptrace has separate fields.
+ * SVE and SME use the same bits for _ONEXEC and _INHERIT.
+ *
+ * flags are as for vec_set_vector_length().
+ */
+static int vec_prctl_status(enum vec_type type, unsigned long flags)
+{
+ int ret;
+
+ if (flags & PR_SVE_SET_VL_ONEXEC)
+ ret = task_get_vl_onexec(current, type);
+ else
+ ret = task_get_vl(current, type);
+
+ if (test_thread_flag(vec_vl_inherit_flag(type)))
+ ret |= PR_SVE_VL_INHERIT;
+
+ return ret;
+}
+
+/* PR_SVE_SET_VL */
+int sve_set_current_vl(unsigned long arg)
+{
+ unsigned long vl, flags;
+ int ret;
+
+ vl = arg & PR_SVE_VL_LEN_MASK;
+ flags = arg & ~vl;
+
+ if (!system_supports_sve() || is_compat_task())
+ return -EINVAL;
+
+ ret = vec_set_vector_length(current, ARM64_VEC_SVE, vl, flags);
+ if (ret)
+ return ret;
+
+ return vec_prctl_status(ARM64_VEC_SVE, flags);
+}
+
+/* PR_SVE_GET_VL */
+int sve_get_current_vl(void)
+{
+ if (!system_supports_sve() || is_compat_task())
+ return -EINVAL;
+
+ return vec_prctl_status(ARM64_VEC_SVE, 0);
+}
+
+#ifdef CONFIG_ARM64_SME
+/* PR_SME_SET_VL */
+int sme_set_current_vl(unsigned long arg)
+{
+ unsigned long vl, flags;
+ int ret;
+
+ vl = arg & PR_SME_VL_LEN_MASK;
+ flags = arg & ~vl;
+
+ if (!system_supports_sme() || is_compat_task())
+ return -EINVAL;
+
+ ret = vec_set_vector_length(current, ARM64_VEC_SME, vl, flags);
+ if (ret)
+ return ret;
+
+ return vec_prctl_status(ARM64_VEC_SME, flags);
+}
+
+/* PR_SME_GET_VL */
+int sme_get_current_vl(void)
+{
+ if (!system_supports_sme() || is_compat_task())
+ return -EINVAL;
+
+ return vec_prctl_status(ARM64_VEC_SME, 0);
+}
+#endif /* CONFIG_ARM64_SME */
+
+static void vec_probe_vqs(struct vl_info *info,
+ DECLARE_BITMAP(map, SVE_VQ_MAX))
+{
+ unsigned int vq, vl;
+
+ bitmap_zero(map, SVE_VQ_MAX);
+
+ for (vq = SVE_VQ_MAX; vq >= SVE_VQ_MIN; --vq) {
+ write_vl(info->type, vq - 1); /* self-syncing */
+
+ switch (info->type) {
+ case ARM64_VEC_SVE:
+ vl = sve_get_vl();
+ break;
+ case ARM64_VEC_SME:
+ vl = sme_get_vl();
+ break;
+ default:
+ vl = 0;
+ break;
+ }
+
+ /* Minimum VL identified? */
+ if (sve_vq_from_vl(vl) > vq)
+ break;
+
+ vq = sve_vq_from_vl(vl); /* skip intervening lengths */
+ set_bit(__vq_to_bit(vq), map);
+ }
+}
+
+/*
+ * Initialise the set of known supported VQs for the boot CPU.
+ * This is called during kernel boot, before secondary CPUs are brought up.
+ */
+void __init vec_init_vq_map(enum vec_type type)
+{
+ struct vl_info *info = &vl_info[type];
+ vec_probe_vqs(info, info->vq_map);
+ bitmap_copy(info->vq_partial_map, info->vq_map, SVE_VQ_MAX);
+}
+
+/*
+ * If we haven't committed to the set of supported VQs yet, filter out
+ * those not supported by the current CPU.
+ * This function is called during the bring-up of early secondary CPUs only.
+ */
+void vec_update_vq_map(enum vec_type type)
+{
+ struct vl_info *info = &vl_info[type];
+ DECLARE_BITMAP(tmp_map, SVE_VQ_MAX);
+
+ vec_probe_vqs(info, tmp_map);
+ bitmap_and(info->vq_map, info->vq_map, tmp_map, SVE_VQ_MAX);
+ bitmap_or(info->vq_partial_map, info->vq_partial_map, tmp_map,
+ SVE_VQ_MAX);
+}
+
+/*
+ * Check whether the current CPU supports all VQs in the committed set.
+ * This function is called during the bring-up of late secondary CPUs only.
+ */
+int vec_verify_vq_map(enum vec_type type)
+{
+ struct vl_info *info = &vl_info[type];
+ DECLARE_BITMAP(tmp_map, SVE_VQ_MAX);
+ unsigned long b;
+
+ vec_probe_vqs(info, tmp_map);
+
+ bitmap_complement(tmp_map, tmp_map, SVE_VQ_MAX);
+ if (bitmap_intersects(tmp_map, info->vq_map, SVE_VQ_MAX)) {
+ pr_warn("%s: cpu%d: Required vector length(s) missing\n",
+ info->name, smp_processor_id());
+ return -EINVAL;
+ }
+
+ if (!IS_ENABLED(CONFIG_KVM) || !is_hyp_mode_available())
+ return 0;
+
+ /*
+ * For KVM, it is necessary to ensure that this CPU doesn't
+ * support any vector length that guests may have probed as
+ * unsupported.
+ */
+
+ /* Recover the set of supported VQs: */
+ bitmap_complement(tmp_map, tmp_map, SVE_VQ_MAX);
+ /* Find VQs supported that are not globally supported: */
+ bitmap_andnot(tmp_map, tmp_map, info->vq_map, SVE_VQ_MAX);
+
+ /* Find the lowest such VQ, if any: */
+ b = find_last_bit(tmp_map, SVE_VQ_MAX);
+ if (b >= SVE_VQ_MAX)
+ return 0; /* no mismatches */
+
+ /*
+ * Mismatches above sve_max_virtualisable_vl are fine, since
+ * no guest is allowed to configure ZCR_EL2.LEN to exceed this:
+ */
+ if (sve_vl_from_vq(__bit_to_vq(b)) <= info->max_virtualisable_vl) {
+ pr_warn("%s: cpu%d: Unsupported vector length(s) present\n",
+ info->name, smp_processor_id());
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static void __init sve_efi_setup(void)
+{
+ int max_vl = 0;
+ int i;
+
+ if (!IS_ENABLED(CONFIG_EFI))
+ return;
+
+ for (i = 0; i < ARRAY_SIZE(vl_info); i++)
+ max_vl = max(vl_info[i].max_vl, max_vl);
+
+ /*
+ * alloc_percpu() warns and prints a backtrace if this goes wrong.
+ * This is evidence of a crippled system and we are returning void,
+ * so no attempt is made to handle this situation here.
+ */
+ if (!sve_vl_valid(max_vl))
+ goto fail;
+
+ efi_sve_state = __alloc_percpu(
+ SVE_SIG_REGS_SIZE(sve_vq_from_vl(max_vl)), SVE_VQ_BYTES);
+ if (!efi_sve_state)
+ goto fail;
+
+ return;
+
+fail:
+ panic("Cannot allocate percpu memory for EFI SVE save/restore");
+}
+
+/*
+ * Enable SVE for EL1.
+ * Intended for use by the cpufeatures code during CPU boot.
+ */
+void sve_kernel_enable(const struct arm64_cpu_capabilities *__always_unused p)
+{
+ write_sysreg(read_sysreg(CPACR_EL1) | CPACR_EL1_ZEN_EL1EN, CPACR_EL1);
+ isb();
+}
+
+/*
+ * Read the pseudo-ZCR used by cpufeatures to identify the supported SVE
+ * vector length.
+ *
+ * Use only if SVE is present.
+ * This function clobbers the SVE vector length.
+ */
+u64 read_zcr_features(void)
+{
+ /*
+ * Set the maximum possible VL, and write zeroes to all other
+ * bits to see if they stick.
+ */
+ sve_kernel_enable(NULL);
+ write_sysreg_s(ZCR_ELx_LEN_MASK, SYS_ZCR_EL1);
+
+ /* Return LEN value that would be written to get the maximum VL */
+ return sve_vq_from_vl(sve_get_vl()) - 1;
+}
+
+void __init sve_setup(void)
+{
+ struct vl_info *info = &vl_info[ARM64_VEC_SVE];
+ u64 zcr;
+ DECLARE_BITMAP(tmp_map, SVE_VQ_MAX);
+ unsigned long b;
+
+ if (!system_supports_sve())
+ return;
+
+ /*
+ * The SVE architecture mandates support for 128-bit vectors,
+ * so sve_vq_map must have at least SVE_VQ_MIN set.
+ * If something went wrong, at least try to patch it up:
+ */
+ if (WARN_ON(!test_bit(__vq_to_bit(SVE_VQ_MIN), info->vq_map)))
+ set_bit(__vq_to_bit(SVE_VQ_MIN), info->vq_map);
+
+ zcr = read_sanitised_ftr_reg(SYS_ZCR_EL1);
+ info->max_vl = sve_vl_from_vq((zcr & ZCR_ELx_LEN_MASK) + 1);
+
+ /*
+ * Sanity-check that the max VL we determined through CPU features
+ * corresponds properly to sve_vq_map. If not, do our best:
+ */
+ if (WARN_ON(info->max_vl != find_supported_vector_length(ARM64_VEC_SVE,
+ info->max_vl)))
+ info->max_vl = find_supported_vector_length(ARM64_VEC_SVE,
+ info->max_vl);
+
+ /*
+ * For the default VL, pick the maximum supported value <= 64.
+ * VL == 64 is guaranteed not to grow the signal frame.
+ */
+ set_sve_default_vl(find_supported_vector_length(ARM64_VEC_SVE, 64));
+
+ bitmap_andnot(tmp_map, info->vq_partial_map, info->vq_map,
+ SVE_VQ_MAX);
+
+ b = find_last_bit(tmp_map, SVE_VQ_MAX);
+ if (b >= SVE_VQ_MAX)
+ /* No non-virtualisable VLs found */
+ info->max_virtualisable_vl = SVE_VQ_MAX;
+ else if (WARN_ON(b == SVE_VQ_MAX - 1))
+ /* No virtualisable VLs? This is architecturally forbidden. */
+ info->max_virtualisable_vl = SVE_VQ_MIN;
+ else /* b + 1 < SVE_VQ_MAX */
+ info->max_virtualisable_vl = sve_vl_from_vq(__bit_to_vq(b + 1));
+
+ if (info->max_virtualisable_vl > info->max_vl)
+ info->max_virtualisable_vl = info->max_vl;
+
+ pr_info("%s: maximum available vector length %u bytes per vector\n",
+ info->name, info->max_vl);
+ pr_info("%s: default vector length %u bytes per vector\n",
+ info->name, get_sve_default_vl());
+
+ /* KVM decides whether to support mismatched systems. Just warn here: */
+ if (sve_max_virtualisable_vl() < sve_max_vl())
+ pr_warn("%s: unvirtualisable vector lengths present\n",
+ info->name);
+
+ sve_efi_setup();
+}
+
+/*
+ * Called from the put_task_struct() path, which cannot get here
+ * unless dead_task is really dead and not schedulable.
+ */
+void fpsimd_release_task(struct task_struct *dead_task)
+{
+ __sve_free(dead_task);
+ sme_free(dead_task);
+}
+
+#endif /* CONFIG_ARM64_SVE */
+
+#ifdef CONFIG_ARM64_SME
+
+/*
+ * Ensure that task->thread.za_state is allocated and sufficiently large.
+ *
+ * This function should be used only in preparation for replacing
+ * task->thread.za_state with new data. The memory is always zeroed
+ * here to prevent stale data from showing through: this is done in
+ * the interest of testability and predictability, the architecture
+ * guarantees that when ZA is enabled it will be zeroed.
+ */
+void sme_alloc(struct task_struct *task, bool flush)
+{
+ if (task->thread.za_state && flush) {
+ memset(task->thread.za_state, 0, za_state_size(task));
+ return;
+ }
+
+ /* This could potentially be up to 64K. */
+ task->thread.za_state =
+ kzalloc(za_state_size(task), GFP_KERNEL);
+}
+
+static void sme_free(struct task_struct *task)
+{
+ kfree(task->thread.za_state);
+ task->thread.za_state = NULL;
+}
+
+void sme_kernel_enable(const struct arm64_cpu_capabilities *__always_unused p)
+{
+ /* Set priority for all PEs to architecturally defined minimum */
+ write_sysreg_s(read_sysreg_s(SYS_SMPRI_EL1) & ~SMPRI_EL1_PRIORITY_MASK,
+ SYS_SMPRI_EL1);
+
+ /* Allow SME in kernel */
+ write_sysreg(read_sysreg(CPACR_EL1) | CPACR_EL1_SMEN_EL1EN, CPACR_EL1);
+ isb();
+
+ /* Allow EL0 to access TPIDR2 */
+ write_sysreg(read_sysreg(SCTLR_EL1) | SCTLR_ELx_ENTP2, SCTLR_EL1);
+ isb();
+}
+
+/*
+ * This must be called after sme_kernel_enable(), we rely on the
+ * feature table being sorted to ensure this.
+ */
+void fa64_kernel_enable(const struct arm64_cpu_capabilities *__always_unused p)
+{
+ /* Allow use of FA64 */
+ write_sysreg_s(read_sysreg_s(SYS_SMCR_EL1) | SMCR_ELx_FA64_MASK,
+ SYS_SMCR_EL1);
+}
+
+/*
+ * Read the pseudo-SMCR used by cpufeatures to identify the supported
+ * vector length.
+ *
+ * Use only if SME is present.
+ * This function clobbers the SME vector length.
+ */
+u64 read_smcr_features(void)
+{
+ sme_kernel_enable(NULL);
+
+ /*
+ * Set the maximum possible VL.
+ */
+ write_sysreg_s(read_sysreg_s(SYS_SMCR_EL1) | SMCR_ELx_LEN_MASK,
+ SYS_SMCR_EL1);
+
+ /* Return LEN value that would be written to get the maximum VL */
+ return sve_vq_from_vl(sme_get_vl()) - 1;
+}
+
+void __init sme_setup(void)
+{
+ struct vl_info *info = &vl_info[ARM64_VEC_SME];
+ u64 smcr;
+ int min_bit;
+
+ if (!system_supports_sme())
+ return;
+
+ /*
+ * SME doesn't require any particular vector length be
+ * supported but it does require at least one. We should have
+ * disabled the feature entirely while bringing up CPUs but
+ * let's double check here.
+ */
+ WARN_ON(bitmap_empty(info->vq_map, SVE_VQ_MAX));
+
+ min_bit = find_last_bit(info->vq_map, SVE_VQ_MAX);
+ info->min_vl = sve_vl_from_vq(__bit_to_vq(min_bit));
+
+ smcr = read_sanitised_ftr_reg(SYS_SMCR_EL1);
+ info->max_vl = sve_vl_from_vq((smcr & SMCR_ELx_LEN_MASK) + 1);
+
+ /*
+ * Sanity-check that the max VL we determined through CPU features
+ * corresponds properly to sme_vq_map. If not, do our best:
+ */
+ if (WARN_ON(info->max_vl != find_supported_vector_length(ARM64_VEC_SME,
+ info->max_vl)))
+ info->max_vl = find_supported_vector_length(ARM64_VEC_SME,
+ info->max_vl);
+
+ WARN_ON(info->min_vl > info->max_vl);
+
+ /*
+ * For the default VL, pick the maximum supported value <= 32
+ * (256 bits) if there is one since this is guaranteed not to
+ * grow the signal frame when in streaming mode, otherwise the
+ * minimum available VL will be used.
+ */
+ set_sme_default_vl(find_supported_vector_length(ARM64_VEC_SME, 32));
+
+ pr_info("SME: minimum available vector length %u bytes per vector\n",
+ info->min_vl);
+ pr_info("SME: maximum available vector length %u bytes per vector\n",
+ info->max_vl);
+ pr_info("SME: default vector length %u bytes per vector\n",
+ get_sme_default_vl());
+}
+
+#endif /* CONFIG_ARM64_SME */
+
+static void sve_init_regs(void)
+{
+ /*
+ * Convert the FPSIMD state to SVE, zeroing all the state that
+ * is not shared with FPSIMD. If (as is likely) the current
+ * state is live in the registers then do this there and
+ * update our metadata for the current task including
+ * disabling the trap, otherwise update our in-memory copy.
+ * We are guaranteed to not be in streaming mode, we can only
+ * take a SVE trap when not in streaming mode and we can't be
+ * in streaming mode when taking a SME trap.
+ */
+ if (!test_thread_flag(TIF_FOREIGN_FPSTATE)) {
+ unsigned long vq_minus_one =
+ sve_vq_from_vl(task_get_sve_vl(current)) - 1;
+ sve_set_vq(vq_minus_one);
+ sve_flush_live(true, vq_minus_one);
+ fpsimd_bind_task_to_cpu();
+ } else {
+ fpsimd_to_sve(current);
+ }
+}
+
+/*
+ * Trapped SVE access
+ *
+ * Storage is allocated for the full SVE state, the current FPSIMD
+ * register contents are migrated across, and the access trap is
+ * disabled.
+ *
+ * TIF_SVE should be clear on entry: otherwise, fpsimd_restore_current_state()
+ * would have disabled the SVE access trap for userspace during
+ * ret_to_user, making an SVE access trap impossible in that case.
+ */
+void do_sve_acc(unsigned long esr, struct pt_regs *regs)
+{
+ /* Even if we chose not to use SVE, the hardware could still trap: */
+ if (unlikely(!system_supports_sve()) || WARN_ON(is_compat_task())) {
+ force_signal_inject(SIGILL, ILL_ILLOPC, regs->pc, 0);
+ return;
+ }
+
+ sve_alloc(current, true);
+ if (!current->thread.sve_state) {
+ force_sig(SIGKILL);
+ return;
+ }
+
+ get_cpu_fpsimd_context();
+
+ if (test_and_set_thread_flag(TIF_SVE))
+ WARN_ON(1); /* SVE access shouldn't have trapped */
+
+ /*
+ * Even if the task can have used streaming mode we can only
+ * generate SVE access traps in normal SVE mode and
+ * transitioning out of streaming mode may discard any
+ * streaming mode state. Always clear the high bits to avoid
+ * any potential errors tracking what is properly initialised.
+ */
+ sve_init_regs();
+
+ put_cpu_fpsimd_context();
+}
+
+/*
+ * Trapped SME access
+ *
+ * Storage is allocated for the full SVE and SME state, the current
+ * FPSIMD register contents are migrated to SVE if SVE is not already
+ * active, and the access trap is disabled.
+ *
+ * TIF_SME should be clear on entry: otherwise, fpsimd_restore_current_state()
+ * would have disabled the SME access trap for userspace during
+ * ret_to_user, making an SVE access trap impossible in that case.
+ */
+void do_sme_acc(unsigned long esr, struct pt_regs *regs)
+{
+ /* Even if we chose not to use SME, the hardware could still trap: */
+ if (unlikely(!system_supports_sme()) || WARN_ON(is_compat_task())) {
+ force_signal_inject(SIGILL, ILL_ILLOPC, regs->pc, 0);
+ return;
+ }
+
+ /*
+ * If this not a trap due to SME being disabled then something
+ * is being used in the wrong mode, report as SIGILL.
+ */
+ if (ESR_ELx_ISS(esr) != ESR_ELx_SME_ISS_SME_DISABLED) {
+ force_signal_inject(SIGILL, ILL_ILLOPC, regs->pc, 0);
+ return;
+ }
+
+ sve_alloc(current, false);
+ sme_alloc(current, true);
+ if (!current->thread.sve_state || !current->thread.za_state) {
+ force_sig(SIGKILL);
+ return;
+ }
+
+ get_cpu_fpsimd_context();
+
+ /* With TIF_SME userspace shouldn't generate any traps */
+ if (test_and_set_thread_flag(TIF_SME))
+ WARN_ON(1);
+
+ if (!test_thread_flag(TIF_FOREIGN_FPSTATE)) {
+ unsigned long vq_minus_one =
+ sve_vq_from_vl(task_get_sme_vl(current)) - 1;
+ sme_set_vq(vq_minus_one);
+
+ fpsimd_bind_task_to_cpu();
+ }
+
+ put_cpu_fpsimd_context();
+}
+
+/*
+ * Trapped FP/ASIMD access.
+ */
+void do_fpsimd_acc(unsigned long esr, struct pt_regs *regs)
+{
+ /* TODO: implement lazy context saving/restoring */
+ WARN_ON(1);
+}
+
+/*
+ * Raise a SIGFPE for the current process.
+ */
+void do_fpsimd_exc(unsigned long esr, struct pt_regs *regs)
+{
+ unsigned int si_code = FPE_FLTUNK;
+
+ if (esr & ESR_ELx_FP_EXC_TFV) {
+ if (esr & FPEXC_IOF)
+ si_code = FPE_FLTINV;
+ else if (esr & FPEXC_DZF)
+ si_code = FPE_FLTDIV;
+ else if (esr & FPEXC_OFF)
+ si_code = FPE_FLTOVF;
+ else if (esr & FPEXC_UFF)
+ si_code = FPE_FLTUND;
+ else if (esr & FPEXC_IXF)
+ si_code = FPE_FLTRES;
+ }
+
+ send_sig_fault(SIGFPE, si_code,
+ (void __user *)instruction_pointer(regs),
+ current);
+}
+
+void fpsimd_thread_switch(struct task_struct *next)
+{
+ bool wrong_task, wrong_cpu;
+
+ if (!system_supports_fpsimd())
+ return;
+
+ __get_cpu_fpsimd_context();
+
+ /* Save unsaved fpsimd state, if any: */
+ fpsimd_save();
+
+ /*
+ * Fix up TIF_FOREIGN_FPSTATE to correctly describe next's
+ * state. For kernel threads, FPSIMD registers are never loaded
+ * and wrong_task and wrong_cpu will always be true.
+ */
+ wrong_task = __this_cpu_read(fpsimd_last_state.st) !=
+ &next->thread.uw.fpsimd_state;
+ wrong_cpu = next->thread.fpsimd_cpu != smp_processor_id();
+
+ update_tsk_thread_flag(next, TIF_FOREIGN_FPSTATE,
+ wrong_task || wrong_cpu);
+
+ __put_cpu_fpsimd_context();
+}
+
+static void fpsimd_flush_thread_vl(enum vec_type type)
+{
+ int vl, supported_vl;
+
+ /*
+ * Reset the task vector length as required. This is where we
+ * ensure that all user tasks have a valid vector length
+ * configured: no kernel task can become a user task without
+ * an exec and hence a call to this function. By the time the
+ * first call to this function is made, all early hardware
+ * probing is complete, so __sve_default_vl should be valid.
+ * If a bug causes this to go wrong, we make some noise and
+ * try to fudge thread.sve_vl to a safe value here.
+ */
+ vl = task_get_vl_onexec(current, type);
+ if (!vl)
+ vl = get_default_vl(type);
+
+ if (WARN_ON(!sve_vl_valid(vl)))
+ vl = vl_info[type].min_vl;
+
+ supported_vl = find_supported_vector_length(type, vl);
+ if (WARN_ON(supported_vl != vl))
+ vl = supported_vl;
+
+ task_set_vl(current, type, vl);
+
+ /*
+ * If the task is not set to inherit, ensure that the vector
+ * length will be reset by a subsequent exec:
+ */
+ if (!test_thread_flag(vec_vl_inherit_flag(type)))
+ task_set_vl_onexec(current, type, 0);
+}
+
+void fpsimd_flush_thread(void)
+{
+ void *sve_state = NULL;
+ void *za_state = NULL;
+
+ if (!system_supports_fpsimd())
+ return;
+
+ get_cpu_fpsimd_context();
+
+ fpsimd_flush_task_state(current);
+ memset(&current->thread.uw.fpsimd_state, 0,
+ sizeof(current->thread.uw.fpsimd_state));
+
+ if (system_supports_sve()) {
+ clear_thread_flag(TIF_SVE);
+
+ /* Defer kfree() while in atomic context */
+ sve_state = current->thread.sve_state;
+ current->thread.sve_state = NULL;
+
+ fpsimd_flush_thread_vl(ARM64_VEC_SVE);
+ }
+
+ if (system_supports_sme()) {
+ clear_thread_flag(TIF_SME);
+
+ /* Defer kfree() while in atomic context */
+ za_state = current->thread.za_state;
+ current->thread.za_state = NULL;
+
+ fpsimd_flush_thread_vl(ARM64_VEC_SME);
+ current->thread.svcr = 0;
+ }
+
+ put_cpu_fpsimd_context();
+ kfree(sve_state);
+ kfree(za_state);
+}
+
+/*
+ * Save the userland FPSIMD state of 'current' to memory, but only if the state
+ * currently held in the registers does in fact belong to 'current'
+ */
+void fpsimd_preserve_current_state(void)
+{
+ if (!system_supports_fpsimd())
+ return;
+
+ get_cpu_fpsimd_context();
+ fpsimd_save();
+ put_cpu_fpsimd_context();
+}
+
+/*
+ * Like fpsimd_preserve_current_state(), but ensure that
+ * current->thread.uw.fpsimd_state is updated so that it can be copied to
+ * the signal frame.
+ */
+void fpsimd_signal_preserve_current_state(void)
+{
+ fpsimd_preserve_current_state();
+ if (test_thread_flag(TIF_SVE))
+ sve_to_fpsimd(current);
+}
+
+/*
+ * Associate current's FPSIMD context with this cpu
+ * The caller must have ownership of the cpu FPSIMD context before calling
+ * this function.
+ */
+static void fpsimd_bind_task_to_cpu(void)
+{
+ struct fpsimd_last_state_struct *last =
+ this_cpu_ptr(&fpsimd_last_state);
+
+ WARN_ON(!system_supports_fpsimd());
+ last->st = &current->thread.uw.fpsimd_state;
+ last->sve_state = current->thread.sve_state;
+ last->za_state = current->thread.za_state;
+ last->sve_vl = task_get_sve_vl(current);
+ last->sme_vl = task_get_sme_vl(current);
+ last->svcr = &current->thread.svcr;
+ current->thread.fpsimd_cpu = smp_processor_id();
+
+ /*
+ * Toggle SVE and SME trapping for userspace if needed, these
+ * are serialsied by ret_to_user().
+ */
+ if (system_supports_sme()) {
+ if (test_thread_flag(TIF_SME))
+ sme_user_enable();
+ else
+ sme_user_disable();
+ }
+
+ if (system_supports_sve()) {
+ if (test_thread_flag(TIF_SVE))
+ sve_user_enable();
+ else
+ sve_user_disable();
+ }
+}
+
+void fpsimd_bind_state_to_cpu(struct user_fpsimd_state *st, void *sve_state,
+ unsigned int sve_vl, void *za_state,
+ unsigned int sme_vl, u64 *svcr)
+{
+ struct fpsimd_last_state_struct *last =
+ this_cpu_ptr(&fpsimd_last_state);
+
+ WARN_ON(!system_supports_fpsimd());
+ WARN_ON(!in_softirq() && !irqs_disabled());
+
+ last->st = st;
+ last->svcr = svcr;
+ last->sve_state = sve_state;
+ last->za_state = za_state;
+ last->sve_vl = sve_vl;
+ last->sme_vl = sme_vl;
+}
+
+/*
+ * Load the userland FPSIMD state of 'current' from memory, but only if the
+ * FPSIMD state already held in the registers is /not/ the most recent FPSIMD
+ * state of 'current'. This is called when we are preparing to return to
+ * userspace to ensure that userspace sees a good register state.
+ */
+void fpsimd_restore_current_state(void)
+{
+ /*
+ * For the tasks that were created before we detected the absence of
+ * FP/SIMD, the TIF_FOREIGN_FPSTATE could be set via fpsimd_thread_switch(),
+ * e.g, init. This could be then inherited by the children processes.
+ * If we later detect that the system doesn't support FP/SIMD,
+ * we must clear the flag for all the tasks to indicate that the
+ * FPSTATE is clean (as we can't have one) to avoid looping for ever in
+ * do_notify_resume().
+ */
+ if (!system_supports_fpsimd()) {
+ clear_thread_flag(TIF_FOREIGN_FPSTATE);
+ return;
+ }
+
+ get_cpu_fpsimd_context();
+
+ if (test_and_clear_thread_flag(TIF_FOREIGN_FPSTATE)) {
+ task_fpsimd_load();
+ fpsimd_bind_task_to_cpu();
+ }
+
+ put_cpu_fpsimd_context();
+}
+
+/*
+ * Load an updated userland FPSIMD state for 'current' from memory and set the
+ * flag that indicates that the FPSIMD register contents are the most recent
+ * FPSIMD state of 'current'. This is used by the signal code to restore the
+ * register state when returning from a signal handler in FPSIMD only cases,
+ * any SVE context will be discarded.
+ */
+void fpsimd_update_current_state(struct user_fpsimd_state const *state)
+{
+ if (WARN_ON(!system_supports_fpsimd()))
+ return;
+
+ get_cpu_fpsimd_context();
+
+ current->thread.uw.fpsimd_state = *state;
+ if (test_thread_flag(TIF_SVE))
+ fpsimd_to_sve(current);
+
+ task_fpsimd_load();
+ fpsimd_bind_task_to_cpu();
+
+ clear_thread_flag(TIF_FOREIGN_FPSTATE);
+
+ put_cpu_fpsimd_context();
+}
+
+/*
+ * Invalidate live CPU copies of task t's FPSIMD state
+ *
+ * This function may be called with preemption enabled. The barrier()
+ * ensures that the assignment to fpsimd_cpu is visible to any
+ * preemption/softirq that could race with set_tsk_thread_flag(), so
+ * that TIF_FOREIGN_FPSTATE cannot be spuriously re-cleared.
+ *
+ * The final barrier ensures that TIF_FOREIGN_FPSTATE is seen set by any
+ * subsequent code.
+ */
+void fpsimd_flush_task_state(struct task_struct *t)
+{
+ t->thread.fpsimd_cpu = NR_CPUS;
+ /*
+ * If we don't support fpsimd, bail out after we have
+ * reset the fpsimd_cpu for this task and clear the
+ * FPSTATE.
+ */
+ if (!system_supports_fpsimd())
+ return;
+ barrier();
+ set_tsk_thread_flag(t, TIF_FOREIGN_FPSTATE);
+
+ barrier();
+}
+
+/*
+ * Invalidate any task's FPSIMD state that is present on this cpu.
+ * The FPSIMD context should be acquired with get_cpu_fpsimd_context()
+ * before calling this function.
+ */
+static void fpsimd_flush_cpu_state(void)
+{
+ WARN_ON(!system_supports_fpsimd());
+ __this_cpu_write(fpsimd_last_state.st, NULL);
+
+ /*
+ * Leaving streaming mode enabled will cause issues for any kernel
+ * NEON and leaving streaming mode or ZA enabled may increase power
+ * consumption.
+ */
+ if (system_supports_sme())
+ sme_smstop();
+
+ set_thread_flag(TIF_FOREIGN_FPSTATE);
+}
+
+/*
+ * Save the FPSIMD state to memory and invalidate cpu view.
+ * This function must be called with preemption disabled.
+ */
+void fpsimd_save_and_flush_cpu_state(void)
+{
+ if (!system_supports_fpsimd())
+ return;
+ WARN_ON(preemptible());
+ __get_cpu_fpsimd_context();
+ fpsimd_save();
+ fpsimd_flush_cpu_state();
+ __put_cpu_fpsimd_context();
+}
+
+#ifdef CONFIG_KERNEL_MODE_NEON
+
+/*
+ * Kernel-side NEON support functions
+ */
+
+/*
+ * kernel_neon_begin(): obtain the CPU FPSIMD registers for use by the calling
+ * context
+ *
+ * Must not be called unless may_use_simd() returns true.
+ * Task context in the FPSIMD registers is saved back to memory as necessary.
+ *
+ * A matching call to kernel_neon_end() must be made before returning from the
+ * calling context.
+ *
+ * The caller may freely use the FPSIMD registers until kernel_neon_end() is
+ * called.
+ */
+void kernel_neon_begin(void)
+{
+ if (WARN_ON(!system_supports_fpsimd()))
+ return;
+
+ BUG_ON(!may_use_simd());
+
+ get_cpu_fpsimd_context();
+
+ /* Save unsaved fpsimd state, if any: */
+ fpsimd_save();
+
+ /* Invalidate any task state remaining in the fpsimd regs: */
+ fpsimd_flush_cpu_state();
+}
+EXPORT_SYMBOL(kernel_neon_begin);
+
+/*
+ * kernel_neon_end(): give the CPU FPSIMD registers back to the current task
+ *
+ * Must be called from a context in which kernel_neon_begin() was previously
+ * called, with no call to kernel_neon_end() in the meantime.
+ *
+ * The caller must not use the FPSIMD registers after this function is called,
+ * unless kernel_neon_begin() is called again in the meantime.
+ */
+void kernel_neon_end(void)
+{
+ if (!system_supports_fpsimd())
+ return;
+
+ put_cpu_fpsimd_context();
+}
+EXPORT_SYMBOL(kernel_neon_end);
+
+#ifdef CONFIG_EFI
+
+static DEFINE_PER_CPU(struct user_fpsimd_state, efi_fpsimd_state);
+static DEFINE_PER_CPU(bool, efi_fpsimd_state_used);
+static DEFINE_PER_CPU(bool, efi_sve_state_used);
+static DEFINE_PER_CPU(bool, efi_sm_state);
+
+/*
+ * EFI runtime services support functions
+ *
+ * The ABI for EFI runtime services allows EFI to use FPSIMD during the call.
+ * This means that for EFI (and only for EFI), we have to assume that FPSIMD
+ * is always used rather than being an optional accelerator.
+ *
+ * These functions provide the necessary support for ensuring FPSIMD
+ * save/restore in the contexts from which EFI is used.
+ *
+ * Do not use them for any other purpose -- if tempted to do so, you are
+ * either doing something wrong or you need to propose some refactoring.
+ */
+
+/*
+ * __efi_fpsimd_begin(): prepare FPSIMD for making an EFI runtime services call
+ */
+void __efi_fpsimd_begin(void)
+{
+ if (!system_supports_fpsimd())
+ return;
+
+ WARN_ON(preemptible());
+
+ if (may_use_simd()) {
+ kernel_neon_begin();
+ } else {
+ /*
+ * If !efi_sve_state, SVE can't be in use yet and doesn't need
+ * preserving:
+ */
+ if (system_supports_sve() && likely(efi_sve_state)) {
+ char *sve_state = this_cpu_ptr(efi_sve_state);
+ bool ffr = true;
+ u64 svcr;
+
+ __this_cpu_write(efi_sve_state_used, true);
+
+ if (system_supports_sme()) {
+ svcr = read_sysreg_s(SYS_SVCR);
+
+ __this_cpu_write(efi_sm_state,
+ svcr & SVCR_SM_MASK);
+
+ /*
+ * Unless we have FA64 FFR does not
+ * exist in streaming mode.
+ */
+ if (!system_supports_fa64())
+ ffr = !(svcr & SVCR_SM_MASK);
+ }
+
+ sve_save_state(sve_state + sve_ffr_offset(sve_max_vl()),
+ &this_cpu_ptr(&efi_fpsimd_state)->fpsr,
+ ffr);
+
+ if (system_supports_sme())
+ sysreg_clear_set_s(SYS_SVCR,
+ SVCR_SM_MASK, 0);
+
+ } else {
+ fpsimd_save_state(this_cpu_ptr(&efi_fpsimd_state));
+ }
+
+ __this_cpu_write(efi_fpsimd_state_used, true);
+ }
+}
+
+/*
+ * __efi_fpsimd_end(): clean up FPSIMD after an EFI runtime services call
+ */
+void __efi_fpsimd_end(void)
+{
+ if (!system_supports_fpsimd())
+ return;
+
+ if (!__this_cpu_xchg(efi_fpsimd_state_used, false)) {
+ kernel_neon_end();
+ } else {
+ if (system_supports_sve() &&
+ likely(__this_cpu_read(efi_sve_state_used))) {
+ char const *sve_state = this_cpu_ptr(efi_sve_state);
+ bool ffr = true;
+
+ /*
+ * Restore streaming mode; EFI calls are
+ * normal function calls so should not return in
+ * streaming mode.
+ */
+ if (system_supports_sme()) {
+ if (__this_cpu_read(efi_sm_state)) {
+ sysreg_clear_set_s(SYS_SVCR,
+ 0,
+ SVCR_SM_MASK);
+
+ /*
+ * Unless we have FA64 FFR does not
+ * exist in streaming mode.
+ */
+ if (!system_supports_fa64())
+ ffr = false;
+ }
+ }
+
+ sve_load_state(sve_state + sve_ffr_offset(sve_max_vl()),
+ &this_cpu_ptr(&efi_fpsimd_state)->fpsr,
+ ffr);
+
+ __this_cpu_write(efi_sve_state_used, false);
+ } else {
+ fpsimd_load_state(this_cpu_ptr(&efi_fpsimd_state));
+ }
+ }
+}
+
+#endif /* CONFIG_EFI */
+
+#endif /* CONFIG_KERNEL_MODE_NEON */
+
+#ifdef CONFIG_CPU_PM
+static int fpsimd_cpu_pm_notifier(struct notifier_block *self,
+ unsigned long cmd, void *v)
+{
+ switch (cmd) {
+ case CPU_PM_ENTER:
+ fpsimd_save_and_flush_cpu_state();
+ break;
+ case CPU_PM_EXIT:
+ break;
+ case CPU_PM_ENTER_FAILED:
+ default:
+ return NOTIFY_DONE;
+ }
+ return NOTIFY_OK;
+}
+
+static struct notifier_block fpsimd_cpu_pm_notifier_block = {
+ .notifier_call = fpsimd_cpu_pm_notifier,
+};
+
+static void __init fpsimd_pm_init(void)
+{
+ cpu_pm_register_notifier(&fpsimd_cpu_pm_notifier_block);
+}
+
+#else
+static inline void fpsimd_pm_init(void) { }
+#endif /* CONFIG_CPU_PM */
+
+#ifdef CONFIG_HOTPLUG_CPU
+static int fpsimd_cpu_dead(unsigned int cpu)
+{
+ per_cpu(fpsimd_last_state.st, cpu) = NULL;
+ return 0;
+}
+
+static inline void fpsimd_hotplug_init(void)
+{
+ cpuhp_setup_state_nocalls(CPUHP_ARM64_FPSIMD_DEAD, "arm64/fpsimd:dead",
+ NULL, fpsimd_cpu_dead);
+}
+
+#else
+static inline void fpsimd_hotplug_init(void) { }
+#endif
+
+/*
+ * FP/SIMD support code initialisation.
+ */
+static int __init fpsimd_init(void)
+{
+ if (cpu_have_named_feature(FP)) {
+ fpsimd_pm_init();
+ fpsimd_hotplug_init();
+ } else {
+ pr_notice("Floating-point is not implemented\n");
+ }
+
+ if (!cpu_have_named_feature(ASIMD))
+ pr_notice("Advanced SIMD is not implemented\n");
+
+
+ if (cpu_have_named_feature(SME) && !cpu_have_named_feature(SVE))
+ pr_notice("SME is implemented but not SVE\n");
+
+ sve_sysctl_init();
+ sme_sysctl_init();
+
+ return 0;
+}
+core_initcall(fpsimd_init);