Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 865 insertions, 0 deletions

diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c
new file mode 100644
index 000000000..1d190761d
--- /dev/null
+++ b/arch/x86/kernel/fpu/core.c
@@ -0,0 +1,865 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  Copyright (C) 1994 Linus Torvalds
+ *
+ *  Pentium III FXSR, SSE support
+ *  General FPU state handling cleanups
+ *	Gareth Hughes <gareth@valinux.com>, May 2000
+ */
+#include <asm/fpu/api.h>
+#include <asm/fpu/regset.h>
+#include <asm/fpu/sched.h>
+#include <asm/fpu/signal.h>
+#include <asm/fpu/types.h>
+#include <asm/traps.h>
+#include <asm/irq_regs.h>
+
+#include <uapi/asm/kvm.h>
+
+#include <linux/hardirq.h>
+#include <linux/pkeys.h>
+#include <linux/vmalloc.h>
+
+#include "context.h"
+#include "internal.h"
+#include "legacy.h"
+#include "xstate.h"
+
+#define CREATE_TRACE_POINTS
+#include <asm/trace/fpu.h>
+
+#ifdef CONFIG_X86_64
+DEFINE_STATIC_KEY_FALSE(__fpu_state_size_dynamic);
+DEFINE_PER_CPU(u64, xfd_state);
+#endif
+
+/* The FPU state configuration data for kernel and user space */
+struct fpu_state_config	fpu_kernel_cfg __ro_after_init;
+struct fpu_state_config fpu_user_cfg __ro_after_init;
+
+/*
+ * Represents the initial FPU state. It's mostly (but not completely) zeroes,
+ * depending on the FPU hardware format:
+ */
+struct fpstate init_fpstate __ro_after_init;
+
+/* Track in-kernel FPU usage */
+static DEFINE_PER_CPU(bool, in_kernel_fpu);
+
+/*
+ * Track which context is using the FPU on the CPU:
+ */
+DEFINE_PER_CPU(struct fpu *, fpu_fpregs_owner_ctx);
+
+/*
+ * Can we use the FPU in kernel mode with the
+ * whole "kernel_fpu_begin/end()" sequence?
+ */
+bool irq_fpu_usable(void)
+{
+	if (WARN_ON_ONCE(in_nmi()))
+		return false;
+
+	/* In kernel FPU usage already active? */
+	if (this_cpu_read(in_kernel_fpu))
+		return false;
+
+	/*
+	 * When not in NMI or hard interrupt context, FPU can be used in:
+	 *
+	 * - Task context except from within fpregs_lock()'ed critical
+	 *   regions.
+	 *
+	 * - Soft interrupt processing context which cannot happen
+	 *   while in a fpregs_lock()'ed critical region.
+	 */
+	if (!in_hardirq())
+		return true;
+
+	/*
+	 * In hard interrupt context it's safe when soft interrupts
+	 * are enabled, which means the interrupt did not hit in
+	 * a fpregs_lock()'ed critical region.
+	 */
+	return !softirq_count();
+}
+EXPORT_SYMBOL(irq_fpu_usable);
+
+/*
+ * Track AVX512 state use because it is known to slow the max clock
+ * speed of the core.
+ */
+static void update_avx_timestamp(struct fpu *fpu)
+{
+
+#define AVX512_TRACKING_MASK	(XFEATURE_MASK_ZMM_Hi256 | XFEATURE_MASK_Hi16_ZMM)
+
+	if (fpu->fpstate->regs.xsave.header.xfeatures & AVX512_TRACKING_MASK)
+		fpu->avx512_timestamp = jiffies;
+}
+
+/*
+ * Save the FPU register state in fpu->fpstate->regs. The register state is
+ * preserved.
+ *
+ * Must be called with fpregs_lock() held.
+ *
+ * The legacy FNSAVE instruction clears all FPU state unconditionally, so
+ * register state has to be reloaded. That might be a pointless exercise
+ * when the FPU is going to be used by another task right after that. But
+ * this only affects 20+ years old 32bit systems and avoids conditionals all
+ * over the place.
+ *
+ * FXSAVE and all XSAVE variants preserve the FPU register state.
+ */
+void save_fpregs_to_fpstate(struct fpu *fpu)
+{
+	if (likely(use_xsave())) {
+		os_xsave(fpu->fpstate);
+		update_avx_timestamp(fpu);
+		return;
+	}
+
+	if (likely(use_fxsr())) {
+		fxsave(&fpu->fpstate->regs.fxsave);
+		return;
+	}
+
+	/*
+	 * Legacy FPU register saving, FNSAVE always clears FPU registers,
+	 * so we have to reload them from the memory state.
+	 */
+	asm volatile("fnsave %[fp]; fwait" : [fp] "=m" (fpu->fpstate->regs.fsave));
+	frstor(&fpu->fpstate->regs.fsave);
+}
+
+void restore_fpregs_from_fpstate(struct fpstate *fpstate, u64 mask)
+{
+	/*
+	 * AMD K7/K8 and later CPUs up to Zen don't save/restore
+	 * FDP/FIP/FOP unless an exception is pending. Clear the x87 state
+	 * here by setting it to fixed values.  "m" is a random variable
+	 * that should be in L1.
+	 */
+	if (unlikely(static_cpu_has_bug(X86_BUG_FXSAVE_LEAK))) {
+		asm volatile(
+			"fnclex\n\t"
+			"emms\n\t"
+			"fildl %P[addr]"	/* set F?P to defined value */
+			: : [addr] "m" (fpstate));
+	}
+
+	if (use_xsave()) {
+		/*
+		 * Dynamically enabled features are enabled in XCR0, but
+		 * usage requires also that the corresponding bits in XFD
+		 * are cleared.  If the bits are set then using a related
+		 * instruction will raise #NM. This allows to do the
+		 * allocation of the larger FPU buffer lazy from #NM or if
+		 * the task has no permission to kill it which would happen
+		 * via #UD if the feature is disabled in XCR0.
+		 *
+		 * XFD state is following the same life time rules as
+		 * XSTATE and to restore state correctly XFD has to be
+		 * updated before XRSTORS otherwise the component would
+		 * stay in or go into init state even if the bits are set
+		 * in fpstate::regs::xsave::xfeatures.
+		 */
+		xfd_update_state(fpstate);
+
+		/*
+		 * Restoring state always needs to modify all features
+		 * which are in @mask even if the current task cannot use
+		 * extended features.
+		 *
+		 * So fpstate->xfeatures cannot be used here, because then
+		 * a feature for which the task has no permission but was
+		 * used by the previous task would not go into init state.
+		 */
+		mask = fpu_kernel_cfg.max_features & mask;
+
+		os_xrstor(fpstate, mask);
+	} else {
+		if (use_fxsr())
+			fxrstor(&fpstate->regs.fxsave);
+		else
+			frstor(&fpstate->regs.fsave);
+	}
+}
+
+void fpu_reset_from_exception_fixup(void)
+{
+	restore_fpregs_from_fpstate(&init_fpstate, XFEATURE_MASK_FPSTATE);
+}
+
+#if IS_ENABLED(CONFIG_KVM)
+static void __fpstate_reset(struct fpstate *fpstate, u64 xfd);
+
+static void fpu_init_guest_permissions(struct fpu_guest *gfpu)
+{
+	struct fpu_state_perm *fpuperm;
+	u64 perm;
+
+	if (!IS_ENABLED(CONFIG_X86_64))
+		return;
+
+	spin_lock_irq(&current->sighand->siglock);
+	fpuperm = &current->group_leader->thread.fpu.guest_perm;
+	perm = fpuperm->__state_perm;
+
+	/* First fpstate allocation locks down permissions. */
+	WRITE_ONCE(fpuperm->__state_perm, perm | FPU_GUEST_PERM_LOCKED);
+
+	spin_unlock_irq(&current->sighand->siglock);
+
+	gfpu->perm = perm & ~FPU_GUEST_PERM_LOCKED;
+}
+
+bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu)
+{
+	struct fpstate *fpstate;
+	unsigned int size;
+
+	size = fpu_user_cfg.default_size + ALIGN(offsetof(struct fpstate, regs), 64);
+	fpstate = vzalloc(size);
+	if (!fpstate)
+		return false;
+
+	/* Leave xfd to 0 (the reset value defined by spec) */
+	__fpstate_reset(fpstate, 0);
+	fpstate_init_user(fpstate);
+	fpstate->is_valloc	= true;
+	fpstate->is_guest	= true;
+
+	gfpu->fpstate		= fpstate;
+	gfpu->xfeatures		= fpu_user_cfg.default_features;
+	gfpu->perm		= fpu_user_cfg.default_features;
+
+	/*
+	 * KVM sets the FP+SSE bits in the XSAVE header when copying FPU state
+	 * to userspace, even when XSAVE is unsupported, so that restoring FPU
+	 * state on a different CPU that does support XSAVE can cleanly load
+	 * the incoming state using its natural XSAVE.  In other words, KVM's
+	 * uABI size may be larger than this host's default size.  Conversely,
+	 * the default size should never be larger than KVM's base uABI size;
+	 * all features that can expand the uABI size must be opt-in.
+	 */
+	gfpu->uabi_size		= sizeof(struct kvm_xsave);
+	if (WARN_ON_ONCE(fpu_user_cfg.default_size > gfpu->uabi_size))
+		gfpu->uabi_size = fpu_user_cfg.default_size;
+
+	fpu_init_guest_permissions(gfpu);
+
+	return true;
+}
+EXPORT_SYMBOL_GPL(fpu_alloc_guest_fpstate);
+
+void fpu_free_guest_fpstate(struct fpu_guest *gfpu)
+{
+	struct fpstate *fps = gfpu->fpstate;
+
+	if (!fps)
+		return;
+
+	if (WARN_ON_ONCE(!fps->is_valloc || !fps->is_guest || fps->in_use))
+		return;
+
+	gfpu->fpstate = NULL;
+	vfree(fps);
+}
+EXPORT_SYMBOL_GPL(fpu_free_guest_fpstate);
+
+/*
+  * fpu_enable_guest_xfd_features - Check xfeatures against guest perm and enable
+  * @guest_fpu:         Pointer to the guest FPU container
+  * @xfeatures:         Features requested by guest CPUID
+  *
+  * Enable all dynamic xfeatures according to guest perm and requested CPUID.
+  *
+  * Return: 0 on success, error code otherwise
+  */
+int fpu_enable_guest_xfd_features(struct fpu_guest *guest_fpu, u64 xfeatures)
+{
+	lockdep_assert_preemption_enabled();
+
+	/* Nothing to do if all requested features are already enabled. */
+	xfeatures &= ~guest_fpu->xfeatures;
+	if (!xfeatures)
+		return 0;
+
+	return __xfd_enable_feature(xfeatures, guest_fpu);
+}
+EXPORT_SYMBOL_GPL(fpu_enable_guest_xfd_features);
+
+#ifdef CONFIG_X86_64
+void fpu_update_guest_xfd(struct fpu_guest *guest_fpu, u64 xfd)
+{
+	fpregs_lock();
+	guest_fpu->fpstate->xfd = xfd;
+	if (guest_fpu->fpstate->in_use)
+		xfd_update_state(guest_fpu->fpstate);
+	fpregs_unlock();
+}
+EXPORT_SYMBOL_GPL(fpu_update_guest_xfd);
+
+/**
+ * fpu_sync_guest_vmexit_xfd_state - Synchronize XFD MSR and software state
+ *
+ * Must be invoked from KVM after a VMEXIT before enabling interrupts when
+ * XFD write emulation is disabled. This is required because the guest can
+ * freely modify XFD and the state at VMEXIT is not guaranteed to be the
+ * same as the state on VMENTER. So software state has to be udpated before
+ * any operation which depends on it can take place.
+ *
+ * Note: It can be invoked unconditionally even when write emulation is
+ * enabled for the price of a then pointless MSR read.
+ */
+void fpu_sync_guest_vmexit_xfd_state(void)
+{
+	struct fpstate *fps = current->thread.fpu.fpstate;
+
+	lockdep_assert_irqs_disabled();
+	if (fpu_state_size_dynamic()) {
+		rdmsrl(MSR_IA32_XFD, fps->xfd);
+		__this_cpu_write(xfd_state, fps->xfd);
+	}
+}
+EXPORT_SYMBOL_GPL(fpu_sync_guest_vmexit_xfd_state);
+#endif /* CONFIG_X86_64 */
+
+int fpu_swap_kvm_fpstate(struct fpu_guest *guest_fpu, bool enter_guest)
+{
+	struct fpstate *guest_fps = guest_fpu->fpstate;
+	struct fpu *fpu = &current->thread.fpu;
+	struct fpstate *cur_fps = fpu->fpstate;
+
+	fpregs_lock();
+	if (!cur_fps->is_confidential && !test_thread_flag(TIF_NEED_FPU_LOAD))
+		save_fpregs_to_fpstate(fpu);
+
+	/* Swap fpstate */
+	if (enter_guest) {
+		fpu->__task_fpstate = cur_fps;
+		fpu->fpstate = guest_fps;
+		guest_fps->in_use = true;
+	} else {
+		guest_fps->in_use = false;
+		fpu->fpstate = fpu->__task_fpstate;
+		fpu->__task_fpstate = NULL;
+	}
+
+	cur_fps = fpu->fpstate;
+
+	if (!cur_fps->is_confidential) {
+		/* Includes XFD update */
+		restore_fpregs_from_fpstate(cur_fps, XFEATURE_MASK_FPSTATE);
+	} else {
+		/*
+		 * XSTATE is restored by firmware from encrypted
+		 * memory. Make sure XFD state is correct while
+		 * running with guest fpstate
+		 */
+		xfd_update_state(cur_fps);
+	}
+
+	fpregs_mark_activate();
+	fpregs_unlock();
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fpu_swap_kvm_fpstate);
+
+void fpu_copy_guest_fpstate_to_uabi(struct fpu_guest *gfpu, void *buf,
+				    unsigned int size, u64 xfeatures, u32 pkru)
+{
+	struct fpstate *kstate = gfpu->fpstate;
+	union fpregs_state *ustate = buf;
+	struct membuf mb = { .p = buf, .left = size };
+
+	if (cpu_feature_enabled(X86_FEATURE_XSAVE)) {
+		__copy_xstate_to_uabi_buf(mb, kstate, xfeatures, pkru,
+					  XSTATE_COPY_XSAVE);
+	} else {
+		memcpy(&ustate->fxsave, &kstate->regs.fxsave,
+		       sizeof(ustate->fxsave));
+		/* Make it restorable on a XSAVE enabled host */
+		ustate->xsave.header.xfeatures = XFEATURE_MASK_FPSSE;
+	}
+}
+EXPORT_SYMBOL_GPL(fpu_copy_guest_fpstate_to_uabi);
+
+int fpu_copy_uabi_to_guest_fpstate(struct fpu_guest *gfpu, const void *buf,
+				   u64 xcr0, u32 *vpkru)
+{
+	struct fpstate *kstate = gfpu->fpstate;
+	const union fpregs_state *ustate = buf;
+
+	if (!cpu_feature_enabled(X86_FEATURE_XSAVE)) {
+		if (ustate->xsave.header.xfeatures & ~XFEATURE_MASK_FPSSE)
+			return -EINVAL;
+		if (ustate->fxsave.mxcsr & ~mxcsr_feature_mask)
+			return -EINVAL;
+		memcpy(&kstate->regs.fxsave, &ustate->fxsave, sizeof(ustate->fxsave));
+		return 0;
+	}
+
+	if (ustate->xsave.header.xfeatures & ~xcr0)
+		return -EINVAL;
+
+	/*
+	 * Nullify @vpkru to preserve its current value if PKRU's bit isn't set
+	 * in the header.  KVM's odd ABI is to leave PKRU untouched in this
+	 * case (all other components are eventually re-initialized).
+	 */
+	if (!(ustate->xsave.header.xfeatures & XFEATURE_MASK_PKRU))
+		vpkru = NULL;
+
+	return copy_uabi_from_kernel_to_xstate(kstate, ustate, vpkru);
+}
+EXPORT_SYMBOL_GPL(fpu_copy_uabi_to_guest_fpstate);
+#endif /* CONFIG_KVM */
+
+void kernel_fpu_begin_mask(unsigned int kfpu_mask)
+{
+	preempt_disable();
+
+	WARN_ON_FPU(!irq_fpu_usable());
+	WARN_ON_FPU(this_cpu_read(in_kernel_fpu));
+
+	this_cpu_write(in_kernel_fpu, true);
+
+	if (!(current->flags & (PF_KTHREAD | PF_IO_WORKER)) &&
+	    !test_thread_flag(TIF_NEED_FPU_LOAD)) {
+		set_thread_flag(TIF_NEED_FPU_LOAD);
+		save_fpregs_to_fpstate(&current->thread.fpu);
+	}
+	__cpu_invalidate_fpregs_state();
+
+	/* Put sane initial values into the control registers. */
+	if (likely(kfpu_mask & KFPU_MXCSR) && boot_cpu_has(X86_FEATURE_XMM))
+		ldmxcsr(MXCSR_DEFAULT);
+
+	if (unlikely(kfpu_mask & KFPU_387) && boot_cpu_has(X86_FEATURE_FPU))
+		asm volatile ("fninit");
+}
+EXPORT_SYMBOL_GPL(kernel_fpu_begin_mask);
+
+void kernel_fpu_end(void)
+{
+	WARN_ON_FPU(!this_cpu_read(in_kernel_fpu));
+
+	this_cpu_write(in_kernel_fpu, false);
+	preempt_enable();
+}
+EXPORT_SYMBOL_GPL(kernel_fpu_end);
+
+/*
+ * Sync the FPU register state to current's memory register state when the
+ * current task owns the FPU. The hardware register state is preserved.
+ */
+void fpu_sync_fpstate(struct fpu *fpu)
+{
+	WARN_ON_FPU(fpu != &current->thread.fpu);
+
+	fpregs_lock();
+	trace_x86_fpu_before_save(fpu);
+
+	if (!test_thread_flag(TIF_NEED_FPU_LOAD))
+		save_fpregs_to_fpstate(fpu);
+
+	trace_x86_fpu_after_save(fpu);
+	fpregs_unlock();
+}
+
+static inline unsigned int init_fpstate_copy_size(void)
+{
+	if (!use_xsave())
+		return fpu_kernel_cfg.default_size;
+
+	/* XSAVE(S) just needs the legacy and the xstate header part */
+	return sizeof(init_fpstate.regs.xsave);
+}
+
+static inline void fpstate_init_fxstate(struct fpstate *fpstate)
+{
+	fpstate->regs.fxsave.cwd = 0x37f;
+	fpstate->regs.fxsave.mxcsr = MXCSR_DEFAULT;
+}
+
+/*
+ * Legacy x87 fpstate state init:
+ */
+static inline void fpstate_init_fstate(struct fpstate *fpstate)
+{
+	fpstate->regs.fsave.cwd = 0xffff037fu;
+	fpstate->regs.fsave.swd = 0xffff0000u;
+	fpstate->regs.fsave.twd = 0xffffffffu;
+	fpstate->regs.fsave.fos = 0xffff0000u;
+}
+
+/*
+ * Used in two places:
+ * 1) Early boot to setup init_fpstate for non XSAVE systems
+ * 2) fpu_init_fpstate_user() which is invoked from KVM
+ */
+void fpstate_init_user(struct fpstate *fpstate)
+{
+	if (!cpu_feature_enabled(X86_FEATURE_FPU)) {
+		fpstate_init_soft(&fpstate->regs.soft);
+		return;
+	}
+
+	xstate_init_xcomp_bv(&fpstate->regs.xsave, fpstate->xfeatures);
+
+	if (cpu_feature_enabled(X86_FEATURE_FXSR))
+		fpstate_init_fxstate(fpstate);
+	else
+		fpstate_init_fstate(fpstate);
+}
+
+static void __fpstate_reset(struct fpstate *fpstate, u64 xfd)
+{
+	/* Initialize sizes and feature masks */
+	fpstate->size		= fpu_kernel_cfg.default_size;
+	fpstate->user_size	= fpu_user_cfg.default_size;
+	fpstate->xfeatures	= fpu_kernel_cfg.default_features;
+	fpstate->user_xfeatures	= fpu_user_cfg.default_features;
+	fpstate->xfd		= xfd;
+}
+
+void fpstate_reset(struct fpu *fpu)
+{
+	/* Set the fpstate pointer to the default fpstate */
+	fpu->fpstate = &fpu->__fpstate;
+	__fpstate_reset(fpu->fpstate, init_fpstate.xfd);
+
+	/* Initialize the permission related info in fpu */
+	fpu->perm.__state_perm		= fpu_kernel_cfg.default_features;
+	fpu->perm.__state_size		= fpu_kernel_cfg.default_size;
+	fpu->perm.__user_state_size	= fpu_user_cfg.default_size;
+	/* Same defaults for guests */
+	fpu->guest_perm = fpu->perm;
+}
+
+static inline void fpu_inherit_perms(struct fpu *dst_fpu)
+{
+	if (fpu_state_size_dynamic()) {
+		struct fpu *src_fpu = &current->group_leader->thread.fpu;
+
+		spin_lock_irq(&current->sighand->siglock);
+		/* Fork also inherits the permissions of the parent */
+		dst_fpu->perm = src_fpu->perm;
+		dst_fpu->guest_perm = src_fpu->guest_perm;
+		spin_unlock_irq(&current->sighand->siglock);
+	}
+}
+
+/* Clone current's FPU state on fork */
+int fpu_clone(struct task_struct *dst, unsigned long clone_flags, bool minimal)
+{
+	struct fpu *src_fpu = &current->thread.fpu;
+	struct fpu *dst_fpu = &dst->thread.fpu;
+
+	/* The new task's FPU state cannot be valid in the hardware. */
+	dst_fpu->last_cpu = -1;
+
+	fpstate_reset(dst_fpu);
+
+	if (!cpu_feature_enabled(X86_FEATURE_FPU))
+		return 0;
+
+	/*
+	 * Enforce reload for user space tasks and prevent kernel threads
+	 * from trying to save the FPU registers on context switch.
+	 */
+	set_tsk_thread_flag(dst, TIF_NEED_FPU_LOAD);
+
+	/*
+	 * No FPU state inheritance for kernel threads and IO
+	 * worker threads.
+	 */
+	if (minimal) {
+		/* Clear out the minimal state */
+		memcpy(&dst_fpu->fpstate->regs, &init_fpstate.regs,
+		       init_fpstate_copy_size());
+		return 0;
+	}
+
+	/*
+	 * If a new feature is added, ensure all dynamic features are
+	 * caller-saved from here!
+	 */
+	BUILD_BUG_ON(XFEATURE_MASK_USER_DYNAMIC != XFEATURE_MASK_XTILE_DATA);
+
+	/*
+	 * Save the default portion of the current FPU state into the
+	 * clone. Assume all dynamic features to be defined as caller-
+	 * saved, which enables skipping both the expansion of fpstate
+	 * and the copying of any dynamic state.
+	 *
+	 * Do not use memcpy() when TIF_NEED_FPU_LOAD is set because
+	 * copying is not valid when current uses non-default states.
+	 */
+	fpregs_lock();
+	if (test_thread_flag(TIF_NEED_FPU_LOAD))
+		fpregs_restore_userregs();
+	save_fpregs_to_fpstate(dst_fpu);
+	fpregs_unlock();
+	if (!(clone_flags & CLONE_THREAD))
+		fpu_inherit_perms(dst_fpu);
+
+	/*
+	 * Children never inherit PASID state.
+	 * Force it to have its init value:
+	 */
+	if (use_xsave())
+		dst_fpu->fpstate->regs.xsave.header.xfeatures &= ~XFEATURE_MASK_PASID;
+
+	trace_x86_fpu_copy_src(src_fpu);
+	trace_x86_fpu_copy_dst(dst_fpu);
+
+	return 0;
+}
+
+/*
+ * Whitelist the FPU register state embedded into task_struct for hardened
+ * usercopy.
+ */
+void fpu_thread_struct_whitelist(unsigned long *offset, unsigned long *size)
+{
+	*offset = offsetof(struct thread_struct, fpu.__fpstate.regs);
+	*size = fpu_kernel_cfg.default_size;
+}
+
+/*
+ * Drops current FPU state: deactivates the fpregs and
+ * the fpstate. NOTE: it still leaves previous contents
+ * in the fpregs in the eager-FPU case.
+ *
+ * This function can be used in cases where we know that
+ * a state-restore is coming: either an explicit one,
+ * or a reschedule.
+ */
+void fpu__drop(struct fpu *fpu)
+{
+	preempt_disable();
+
+	if (fpu == &current->thread.fpu) {
+		/* Ignore delayed exceptions from user space */
+		asm volatile("1: fwait\n"
+			     "2:\n"
+			     _ASM_EXTABLE(1b, 2b));
+		fpregs_deactivate(fpu);
+	}
+
+	trace_x86_fpu_dropped(fpu);
+
+	preempt_enable();
+}
+
+/*
+ * Clear FPU registers by setting them up from the init fpstate.
+ * Caller must do fpregs_[un]lock() around it.
+ */
+static inline void restore_fpregs_from_init_fpstate(u64 features_mask)
+{
+	if (use_xsave())
+		os_xrstor(&init_fpstate, features_mask);
+	else if (use_fxsr())
+		fxrstor(&init_fpstate.regs.fxsave);
+	else
+		frstor(&init_fpstate.regs.fsave);
+
+	pkru_write_default();
+}
+
+/*
+ * Reset current->fpu memory state to the init values.
+ */
+static void fpu_reset_fpregs(void)
+{
+	struct fpu *fpu = &current->thread.fpu;
+
+	fpregs_lock();
+	__fpu_invalidate_fpregs_state(fpu);
+	/*
+	 * This does not change the actual hardware registers. It just
+	 * resets the memory image and sets TIF_NEED_FPU_LOAD so a
+	 * subsequent return to usermode will reload the registers from the
+	 * task's memory image.
+	 *
+	 * Do not use fpstate_init() here. Just copy init_fpstate which has
+	 * the correct content already except for PKRU.
+	 *
+	 * PKRU handling does not rely on the xstate when restoring for
+	 * user space as PKRU is eagerly written in switch_to() and
+	 * flush_thread().
+	 */
+	memcpy(&fpu->fpstate->regs, &init_fpstate.regs, init_fpstate_copy_size());
+	set_thread_flag(TIF_NEED_FPU_LOAD);
+	fpregs_unlock();
+}
+
+/*
+ * Reset current's user FPU states to the init states.  current's
+ * supervisor states, if any, are not modified by this function.  The
+ * caller guarantees that the XSTATE header in memory is intact.
+ */
+void fpu__clear_user_states(struct fpu *fpu)
+{
+	WARN_ON_FPU(fpu != &current->thread.fpu);
+
+	fpregs_lock();
+	if (!cpu_feature_enabled(X86_FEATURE_FPU)) {
+		fpu_reset_fpregs();
+		fpregs_unlock();
+		return;
+	}
+
+	/*
+	 * Ensure that current's supervisor states are loaded into their
+	 * corresponding registers.
+	 */
+	if (xfeatures_mask_supervisor() &&
+	    !fpregs_state_valid(fpu, smp_processor_id()))
+		os_xrstor_supervisor(fpu->fpstate);
+
+	/* Reset user states in registers. */
+	restore_fpregs_from_init_fpstate(XFEATURE_MASK_USER_RESTORE);
+
+	/*
+	 * Now all FPU registers have their desired values.  Inform the FPU
+	 * state machine that current's FPU registers are in the hardware
+	 * registers. The memory image does not need to be updated because
+	 * any operation relying on it has to save the registers first when
+	 * current's FPU is marked active.
+	 */
+	fpregs_mark_activate();
+	fpregs_unlock();
+}
+
+void fpu_flush_thread(void)
+{
+	fpstate_reset(&current->thread.fpu);
+	fpu_reset_fpregs();
+}
+/*
+ * Load FPU context before returning to userspace.
+ */
+void switch_fpu_return(void)
+{
+	if (!static_cpu_has(X86_FEATURE_FPU))
+		return;
+
+	fpregs_restore_userregs();
+}
+EXPORT_SYMBOL_GPL(switch_fpu_return);
+
+#ifdef CONFIG_X86_DEBUG_FPU
+/*
+ * If current FPU state according to its tracking (loaded FPU context on this
+ * CPU) is not valid then we must have TIF_NEED_FPU_LOAD set so the context is
+ * loaded on return to userland.
+ */
+void fpregs_assert_state_consistent(void)
+{
+	struct fpu *fpu = &current->thread.fpu;
+
+	if (test_thread_flag(TIF_NEED_FPU_LOAD))
+		return;
+
+	WARN_ON_FPU(!fpregs_state_valid(fpu, smp_processor_id()));
+}
+EXPORT_SYMBOL_GPL(fpregs_assert_state_consistent);
+#endif
+
+void fpregs_mark_activate(void)
+{
+	struct fpu *fpu = &current->thread.fpu;
+
+	fpregs_activate(fpu);
+	fpu->last_cpu = smp_processor_id();
+	clear_thread_flag(TIF_NEED_FPU_LOAD);
+}
+
+/*
+ * x87 math exception handling:
+ */
+
+int fpu__exception_code(struct fpu *fpu, int trap_nr)
+{
+	int err;
+
+	if (trap_nr == X86_TRAP_MF) {
+		unsigned short cwd, swd;
+		/*
+		 * (~cwd & swd) will mask out exceptions that are not set to unmasked
+		 * status.  0x3f is the exception bits in these regs, 0x200 is the
+		 * C1 reg you need in case of a stack fault, 0x040 is the stack
+		 * fault bit.  We should only be taking one exception at a time,
+		 * so if this combination doesn't produce any single exception,
+		 * then we have a bad program that isn't synchronizing its FPU usage
+		 * and it will suffer the consequences since we won't be able to
+		 * fully reproduce the context of the exception.
+		 */
+		if (boot_cpu_has(X86_FEATURE_FXSR)) {
+			cwd = fpu->fpstate->regs.fxsave.cwd;
+			swd = fpu->fpstate->regs.fxsave.swd;
+		} else {
+			cwd = (unsigned short)fpu->fpstate->regs.fsave.cwd;
+			swd = (unsigned short)fpu->fpstate->regs.fsave.swd;
+		}
+
+		err = swd & ~cwd;
+	} else {
+		/*
+		 * The SIMD FPU exceptions are handled a little differently, as there
+		 * is only a single status/control register.  Thus, to determine which
+		 * unmasked exception was caught we must mask the exception mask bits
+		 * at 0x1f80, and then use these to mask the exception bits at 0x3f.
+		 */
+		unsigned short mxcsr = MXCSR_DEFAULT;
+
+		if (boot_cpu_has(X86_FEATURE_XMM))
+			mxcsr = fpu->fpstate->regs.fxsave.mxcsr;
+
+		err = ~(mxcsr >> 7) & mxcsr;
+	}
+
+	if (err & 0x001) {	/* Invalid op */
+		/*
+		 * swd & 0x240 == 0x040: Stack Underflow
+		 * swd & 0x240 == 0x240: Stack Overflow
+		 * User must clear the SF bit (0x40) if set
+		 */
+		return FPE_FLTINV;
+	} else if (err & 0x004) { /* Divide by Zero */
+		return FPE_FLTDIV;
+	} else if (err & 0x008) { /* Overflow */
+		return FPE_FLTOVF;
+	} else if (err & 0x012) { /* Denormal, Underflow */
+		return FPE_FLTUND;
+	} else if (err & 0x020) { /* Precision */
+		return FPE_FLTRES;
+	}
+
+	/*
+	 * If we're using IRQ 13, or supposedly even some trap
+	 * X86_TRAP_MF implementations, it's possible
+	 * we get a spurious trap, which is not an error.
+	 */
+	return 0;
+}
+
+/*
+ * Initialize register state that may prevent from entering low-power idle.
+ * This function will be invoked from the cpuidle driver only when needed.
+ */
+noinstr void fpu_idle_fpregs(void)
+{
+	/* Note: AMX_TILE being enabled implies XGETBV1 support */
+	if (cpu_feature_enabled(X86_FEATURE_AMX_TILE) &&
+	    (xfeatures_in_use() & XFEATURE_MASK_XTILE)) {
+		tile_release();
+		__this_cpu_write(fpu_fpregs_owner_ctx, NULL);
+	}
+}