[patch V2 43/52] x86/fpu: Move FXSAVE_LEAK quirk info __copy_kernel_to_fpregs()

Thomas Gleixner
2021-06-14T16:40:26Z

copy_kernel_to_fpregs() restores all xfeatures but it is also the place
where the AMD FXSAVE_LEAK bug is handled.

That prevents fpregs_restore_userregs() to limit the restored features,
which is required to distangle PKRU and XSTATE handling and also for the
upcoming supervisor state management.

Move the FXSAVE_LEAK quirk into __copy_kernel_to_fpregs() and deinline that
function which has become rather fat.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/include/asm/fpu/internal.h | 25 +------------------------
arch/x86/kernel/fpu/core.c | 26 ++++++++++++++++++++++++++
2 files changed, 27 insertions(+), 24 deletions(-)

--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -399,33 +399,10 @@ static inline int xrstor_from_kernel_err
extern void save_fpregs_to_fpstate(struct fpu *fpu);
extern void copy_fpregs_to_fpstate(struct fpu *fpu);

-static inline void __restore_fpregs_from_fpstate(union fpregs_state *fpstate, u64 mask)
-{
- if (use_xsave()) {
- xrstor_from_kernel(&fpstate->xsave, mask);
- } else {
- if (use_fxsr())
- fxrstor_from_kernel(&fpstate->fxsave);
- else
- frstor_from_kernel(&fpstate->fsave);
- }
-}
+extern void __restore_fpregs_from_fpstate(union fpregs_state *fpstate, u64 mask);

static inline void restore_fpregs_from_fpstate(union fpregs_state *fpstate)
{
- /*
- * AMD K7/K8 CPUs 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));
- }
-
__restore_fpregs_from_fpstate(fpstate, -1);
}

--- a/arch/x86/kernel/fpu/core.c
+++ b/arch/x86/kernel/fpu/core.c
@@ -145,6 +145,32 @@ void copy_fpregs_to_fpstate(struct fpu *
restore_fpregs_from_fpstate(&fpu->state);
}

+void __restore_fpregs_from_fpstate(union fpregs_state *fpstate, u64 mask)
+{
+ /*
+ * AMD K7/K8 CPUs 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()) {
+ xrstor_from_kernel(&fpstate->xsave, mask);
+ } else {
+ if (use_fxsr())
+ fxrstor_from_kernel(&fpstate->fxsave);
+ else
+ frstor_from_kernel(&fpstate->fsave);
+ }
+}
+EXPORT_SYMBOL_GPL(__restore_fpregs_from_fpstate);
+
void kernel_fpu_begin_mask(unsigned int kfpu_mask)
{
preempt_disable();