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Diffstat (limited to '')
| -rw-r--r-- | arch/arm64/kernel/fpsimd.c | 1449 |
1 files changed, 1449 insertions, 0 deletions
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c new file mode 100644 index 000000000..a9bbfb800 --- /dev/null +++ b/arch/arm64/kernel/fpsimd.c @@ -0,0 +1,1449 @@ +// 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/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. + * + * 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; + unsigned int sve_vl; +}; + +static DEFINE_PER_CPU(struct fpsimd_last_state_struct, fpsimd_last_state); + +/* Default VL for tasks that don't set it explicitly: */ +static int __sve_default_vl = -1; + +static int get_sve_default_vl(void) +{ + return READ_ONCE(__sve_default_vl); +} + +#ifdef CONFIG_ARM64_SVE + +static void set_sve_default_vl(int val) +{ + WRITE_ONCE(__sve_default_vl, val); +} + +/* Maximum supported vector length across all CPUs (initially poisoned) */ +int __ro_after_init sve_max_vl = SVE_VL_MIN; +int __ro_after_init sve_max_virtualisable_vl = SVE_VL_MIN; + +/* + * Set of available vector lengths, + * where length vq encoded as bit __vq_to_bit(vq): + */ +__ro_after_init DECLARE_BITMAP(sve_vq_map, SVE_VQ_MAX); +/* Set of vector lengths present on at least one cpu: */ +static __ro_after_init DECLARE_BITMAP(sve_vq_partial_map, SVE_VQ_MAX); + +static void __percpu *efi_sve_state; + +#else /* ! CONFIG_ARM64_SVE */ + +/* Dummy declaration for code that will be optimised out: */ +extern __ro_after_init DECLARE_BITMAP(sve_vq_map, SVE_VQ_MAX); +extern __ro_after_init DECLARE_BITMAP(sve_vq_partial_map, SVE_VQ_MAX); +extern void __percpu *efi_sve_state; + +#endif /* ! CONFIG_ARM64_SVE */ + +DEFINE_PER_CPU(bool, fpsimd_context_busy); +EXPORT_PER_CPU_SYMBOL(fpsimd_context_busy); + +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. + */ +static void get_cpu_fpsimd_context(void) +{ + 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(); + preempt_enable(); +} + +static bool have_cpu_fpsimd_context(void) +{ + return !preemptible() && __this_cpu_read(fpsimd_context_busy); +} + +/* + * 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); +} + +/* + * TIF_SVE controls whether a task can use SVE without trapping while + * in userspace, and also 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 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 in + * task->thread.sve_state, formatted appropriately for vector + * length task->thread.sve_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) +{ + WARN_ON(!system_supports_fpsimd()); + WARN_ON(!have_cpu_fpsimd_context()); + + if (system_supports_sve() && test_thread_flag(TIF_SVE)) + sve_load_state(sve_pffr(¤t->thread), + ¤t->thread.uw.fpsimd_state.fpsr, + sve_vq_from_vl(current->thread.sve_vl) - 1); + else + fpsimd_load_state(¤t->thread.uw.fpsimd_state); +} + +/* + * Ensure FPSIMD/SVE storage in memory for the loaded context is up to + * date with respect to the CPU registers. + */ +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() */ + + WARN_ON(!system_supports_fpsimd()); + WARN_ON(!have_cpu_fpsimd_context()); + + if (!test_thread_flag(TIF_FOREIGN_FPSTATE)) { + if (system_supports_sve() && test_thread_flag(TIF_SVE)) { + if (WARN_ON(sve_get_vl() != last->sve_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(last->sve_vl), + &last->st->fpsr); + } 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(unsigned int vl) +{ + int bit; + int max_vl = sve_max_vl; + + if (WARN_ON(!sve_vl_valid(vl))) + vl = SVE_VL_MIN; + + if (WARN_ON(!sve_vl_valid(max_vl))) + max_vl = SVE_VL_MIN; + + if (vl > max_vl) + vl = max_vl; + + bit = find_next_bit(sve_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 sve_proc_do_default_vl(struct ctl_table *table, int write, + void *buffer, size_t *lenp, loff_t *ppos) +{ + int ret; + int vl = get_sve_default_vl(); + 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 = sve_max_vl; + + if (!sve_vl_valid(vl)) + return -EINVAL; + + set_sve_default_vl(find_supported_vector_length(vl)); + return 0; +} + +static struct ctl_table sve_default_vl_table[] = { + { + .procname = "sve_default_vector_length", + .mode = 0644, + .proc_handler = sve_proc_do_default_vl, + }, + { } +}; + +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) */ + +#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()) + return; + + vq = sve_vq_from_vl(task->thread.sve_vl); + __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; + 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()) + return; + + vq = sve_vq_from_vl(task->thread.sve_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 + +/* + * 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) +{ + return SVE_SIG_REGS_SIZE(sve_vq_from_vl(task->thread.sve_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) +{ + if (task->thread.sve_state) { + 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); + + /* + * If future SVE revisions can have larger vectors though, + * this may cease to be true: + */ + BUG_ON(!task->thread.sve_state); +} + + +/* + * 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)) + 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)) + 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)) + return; + + vq = sve_vq_from_vl(task->thread.sve_vl); + + memset(sst, 0, SVE_SIG_REGS_SIZE(vq)); + __fpsimd_to_sve(sst, fst, vq); +} + +int sve_set_vector_length(struct task_struct *task, + unsigned long vl, unsigned long flags) +{ + 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 SVE 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 > SVE_VL_ARCH_MAX) + vl = SVE_VL_ARCH_MAX; + + vl = find_supported_vector_length(vl); + + if (flags & (PR_SVE_VL_INHERIT | + PR_SVE_SET_VL_ONEXEC)) + task->thread.sve_vl_onexec = vl; + else + /* Reset VL to system default on next exec: */ + task->thread.sve_vl_onexec = 0; + + /* Only actually set the VL if not deferred: */ + if (flags & PR_SVE_SET_VL_ONEXEC) + goto out; + + if (vl == task->thread.sve_vl) + 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 + * non-SVE 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)) + sve_to_fpsimd(task); + + if (task == current) + put_cpu_fpsimd_context(); + + /* + * Force reallocation of task SVE state to the correct size + * on next use: + */ + sve_free(task); + + task->thread.sve_vl = vl; + +out: + update_tsk_thread_flag(task, TIF_SVE_VL_INHERIT, + 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 + * + * flags are as for sve_set_vector_length(). + */ +static int sve_prctl_status(unsigned long flags) +{ + int ret; + + if (flags & PR_SVE_SET_VL_ONEXEC) + ret = current->thread.sve_vl_onexec; + else + ret = current->thread.sve_vl; + + if (test_thread_flag(TIF_SVE_VL_INHERIT)) + 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 = sve_set_vector_length(current, vl, flags); + if (ret) + return ret; + + return sve_prctl_status(flags); +} + +/* PR_SVE_GET_VL */ +int sve_get_current_vl(void) +{ + if (!system_supports_sve() || is_compat_task()) + return -EINVAL; + + return sve_prctl_status(0); +} + +static void sve_probe_vqs(DECLARE_BITMAP(map, SVE_VQ_MAX)) +{ + unsigned int vq, vl; + unsigned long zcr; + + bitmap_zero(map, SVE_VQ_MAX); + + zcr = ZCR_ELx_LEN_MASK; + zcr = read_sysreg_s(SYS_ZCR_EL1) & ~zcr; + + for (vq = SVE_VQ_MAX; vq >= SVE_VQ_MIN; --vq) { + write_sysreg_s(zcr | (vq - 1), SYS_ZCR_EL1); /* self-syncing */ + vl = sve_get_vl(); + 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 sve_init_vq_map(void) +{ + sve_probe_vqs(sve_vq_map); + bitmap_copy(sve_vq_partial_map, sve_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 sve_update_vq_map(void) +{ + DECLARE_BITMAP(tmp_map, SVE_VQ_MAX); + + sve_probe_vqs(tmp_map); + bitmap_and(sve_vq_map, sve_vq_map, tmp_map, SVE_VQ_MAX); + bitmap_or(sve_vq_partial_map, sve_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 sve_verify_vq_map(void) +{ + DECLARE_BITMAP(tmp_map, SVE_VQ_MAX); + unsigned long b; + + sve_probe_vqs(tmp_map); + + bitmap_complement(tmp_map, tmp_map, SVE_VQ_MAX); + if (bitmap_intersects(tmp_map, sve_vq_map, SVE_VQ_MAX)) { + pr_warn("SVE: cpu%d: Required vector length(s) missing\n", + 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, sve_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)) <= sve_max_virtualisable_vl) { + pr_warn("SVE: cpu%d: Unsupported vector length(s) present\n", + smp_processor_id()); + return -EINVAL; + } + + return 0; +} + +static void __init sve_efi_setup(void) +{ + if (!IS_ENABLED(CONFIG_EFI)) + return; + + /* + * 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(sve_max_vl)) + goto fail; + + efi_sve_state = __alloc_percpu( + SVE_SIG_REGS_SIZE(sve_vq_from_vl(sve_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) +{ + u64 zcr; + unsigned int vq_max; + + /* + * 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); + + zcr = read_sysreg_s(SYS_ZCR_EL1); + zcr &= ~(u64)ZCR_ELx_LEN_MASK; /* find sticky 1s outside LEN field */ + vq_max = sve_vq_from_vl(sve_get_vl()); + zcr |= vq_max - 1; /* set LEN field to maximum effective value */ + + return zcr; +} + +void __init sve_setup(void) +{ + 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), sve_vq_map))) + set_bit(__vq_to_bit(SVE_VQ_MIN), sve_vq_map); + + zcr = read_sanitised_ftr_reg(SYS_ZCR_EL1); + sve_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(sve_max_vl != find_supported_vector_length(sve_max_vl))) + sve_max_vl = find_supported_vector_length(sve_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(64)); + + bitmap_andnot(tmp_map, sve_vq_partial_map, sve_vq_map, + SVE_VQ_MAX); + + b = find_last_bit(tmp_map, SVE_VQ_MAX); + if (b >= SVE_VQ_MAX) + /* No non-virtualisable VLs found */ + sve_max_virtualisable_vl = SVE_VQ_MAX; + else if (WARN_ON(b == SVE_VQ_MAX - 1)) + /* No virtualisable VLs? This is architecturally forbidden. */ + sve_max_virtualisable_vl = SVE_VQ_MIN; + else /* b + 1 < SVE_VQ_MAX */ + sve_max_virtualisable_vl = sve_vl_from_vq(__bit_to_vq(b + 1)); + + if (sve_max_virtualisable_vl > sve_max_vl) + sve_max_virtualisable_vl = sve_max_vl; + + pr_info("SVE: maximum available vector length %u bytes per vector\n", + sve_max_vl); + pr_info("SVE: default vector length %u bytes per vector\n", + get_sve_default_vl()); + + /* KVM decides whether to support mismatched systems. Just warn here: */ + if (sve_max_virtualisable_vl < sve_max_vl) + pr_warn("SVE: unvirtualisable vector lengths present\n"); + + 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); +} + +#endif /* CONFIG_ARM64_SVE */ + +/* + * Trapped SVE access + * + * Storage is allocated for the full SVE state, the current FPSIMD + * register contents are migrated across, and TIF_SVE is set so that + * the SVE access trap will be disabled the next time this task + * reaches ret_to_user. + * + * 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 int 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); + + get_cpu_fpsimd_context(); + + fpsimd_save(); + + /* Force ret_to_user to reload the registers: */ + fpsimd_flush_task_state(current); + + fpsimd_to_sve(current); + if (test_and_set_thread_flag(TIF_SVE)) + WARN_ON(1); /* SVE access shouldn't have trapped */ + + put_cpu_fpsimd_context(); +} + +/* + * Trapped FP/ASIMD access. + */ +void do_fpsimd_acc(unsigned int 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 int 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(); +} + +void fpsimd_flush_thread(void) +{ + int vl, supported_vl; + + if (!system_supports_fpsimd()) + return; + + get_cpu_fpsimd_context(); + + fpsimd_flush_task_state(current); + memset(¤t->thread.uw.fpsimd_state, 0, + sizeof(current->thread.uw.fpsimd_state)); + + if (system_supports_sve()) { + clear_thread_flag(TIF_SVE); + sve_free(current); + + /* + * 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 = current->thread.sve_vl_onexec ? + current->thread.sve_vl_onexec : get_sve_default_vl(); + + if (WARN_ON(!sve_vl_valid(vl))) + vl = SVE_VL_MIN; + + supported_vl = find_supported_vector_length(vl); + if (WARN_ON(supported_vl != vl)) + vl = supported_vl; + + current->thread.sve_vl = 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(TIF_SVE_VL_INHERIT)) + current->thread.sve_vl_onexec = 0; + } + + put_cpu_fpsimd_context(); +} + +/* + * 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 (system_supports_sve() && 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. + */ +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 = ¤t->thread.uw.fpsimd_state; + last->sve_state = current->thread.sve_state; + last->sve_vl = current->thread.sve_vl; + current->thread.fpsimd_cpu = smp_processor_id(); + + if (system_supports_sve()) { + /* Toggle SVE trapping for userspace if needed */ + if (test_thread_flag(TIF_SVE)) + sve_user_enable(); + else + sve_user_disable(); + + /* Serialised by exception return to user */ + } +} + +void fpsimd_bind_state_to_cpu(struct user_fpsimd_state *st, void *sve_state, + unsigned int sve_vl) +{ + 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->sve_state = sve_state; + last->sve_vl = sve_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' + */ +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' + */ +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 (system_supports_sve() && 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); + 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); + +/* + * 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); + + __this_cpu_write(efi_sve_state_used, true); + + sve_save_state(sve_state + sve_ffr_offset(sve_max_vl), + &this_cpu_ptr(&efi_fpsimd_state)->fpsr); + } 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); + + sve_load_state(sve_state + sve_ffr_offset(sve_max_vl), + &this_cpu_ptr(&efi_fpsimd_state)->fpsr, + sve_vq_from_vl(sve_get_vl()) - 1); + + __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"); + + return sve_sysctl_init(); +} +core_initcall(fpsimd_init); |