[patch 31/31] x86/fpu: Provide a proper function for ex_handler_fprestore()

Thomas Gleixner
2021-10-12T00:07:18Z

To make upcoming changes for support of dynamically enabled features
simpler, provide a proper function for the exception handler which removes
exposure of FPU internals.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/include/asm/fpu/api.h | 4 +---
arch/x86/kernel/fpu/core.c | 5 +++++
arch/x86/kernel/fpu/internal.h | 2 ++
arch/x86/mm/extable.c | 5 ++---
4 files changed, 10 insertions(+), 6 deletions(-)

--- a/arch/x86/include/asm/fpu/api.h
+++ b/arch/x86/include/asm/fpu/api.h
@@ -113,6 +113,7 @@ static inline void update_pasid(void) {
/* Trap handling */
extern int fpu__exception_code(struct fpu *fpu, int trap_nr);
extern void fpu_sync_fpstate(struct fpu *fpu);
+extern void fpu_reset_from_exception_fixup(void);

/* Boot, hotplug and resume */
extern void fpu__init_cpu(void);
@@ -129,9 +130,6 @@ static inline void fpstate_init_soft(str
/* State tracking */
DECLARE_PER_CPU(struct fpu *, fpu_fpregs_owner_ctx);

-/* FPSTATE */
-extern union fpregs_state init_fpstate;
-
/* FPSTATE related functions which are exported to KVM */
extern void fpu_init_fpstate_user(struct fpu *fpu);

--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -155,6 +155,11 @@ void restore_fpregs_from_fpstate(union f
}
}

+void fpu_reset_from_exception_fixup(void)
+{
+ restore_fpregs_from_fpstate(&init_fpstate, xfeatures_mask_fpstate());
+}
+
#if IS_ENABLED(CONFIG_KVM)
void fpu_swap_kvm_fpu(struct fpu *save, struct fpu *rstor, u64 restore_mask)
{
--- a/arch/x86/kernel/fpu/internal.h
+++ b/arch/x86/kernel/fpu/internal.h
@@ -2,6 +2,8 @@
#ifndef __X86_KERNEL_FPU_INTERNAL_H
#define __X86_KERNEL_FPU_INTERNAL_H

+extern union fpregs_state init_fpstate;
+
/* CPU feature check wrappers */
static __always_inline __pure bool use_xsave(void)
{
--- a/arch/x86/mm/extable.c
+++ b/arch/x86/mm/extable.c
@@ -4,8 +4,7 @@
#include <linux/sched/debug.h>
#include <xen/xen.h>

-#include <asm/fpu/signal.h>
-#include <asm/fpu/xstate.h>
+#include <asm/fpu/api.h>
#include <asm/sev.h>
#include <asm/traps.h>
#include <asm/kdebug.h>
@@ -48,7 +47,7 @@ static bool ex_handler_fprestore(const s
WARN_ONCE(1, "Bad FPU state detected at %pB, reinitializing FPU registers.",
(void *)instruction_pointer(regs));

- restore_fpregs_from_fpstate(&init_fpstate, xfeatures_mask_fpstate());
+ fpu_reset_from_exception_fixup();
return true;
}