Messages in this thread Patch in this message | | | From | "Chang S. Bae" <> | Subject | [PATCH v7 26/26] x86/fpu/xstate: Add a sanity check for XFD state when saving XSTATE | Date | Sat, 10 Jul 2021 06:03:13 -0700 |
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Add a DEBUG sanity check that XFD state matches with XINUSE state.
Instead of reading MSR IA32_XFD directly, read a per-cpu value that is recorded at every MSR write.
Suggested-by: Dave Hansen <dave.hansen@linux.intel.com> Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com> Reviewed-by: Len Brown <len.brown@intel.com> Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org --- Changes from v5: * Added as a new patch. (Dave Hansen) --- arch/x86/include/asm/fpu/internal.h | 15 +++++++++++++++ arch/x86/kernel/fpu/core.c | 13 +++++++++++++ 2 files changed, 28 insertions(+)
diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h index c9f1573f3ff8..1b3062d5f5a0 100644 --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -570,10 +570,25 @@ static inline void switch_fpu_prepare(struct fpu *old_fpu, int cpu) /* The Extended Feature Disable (XFD) helpers: */ +#ifdef CONFIG_X86_DEBUG_FPU +DECLARE_PER_CPU(u64, xfd_shadow); +static inline u64 xfd_debug_shadow(void) +{ + return this_cpu_read(xfd_shadow); +} + +static inline void xfd_write(u64 value) +{ + wrmsrl_safe(MSR_IA32_XFD, value); + this_cpu_write(xfd_shadow, value); +} +#else +#define xfd_debug_shadow() 0 static inline void xfd_write(u64 value) { wrmsrl_safe(MSR_IA32_XFD, value); } +#endif static inline u64 xfd_read(void) { diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index e8912b5b9369..1b1306488fb6 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -82,6 +82,10 @@ bool irq_fpu_usable(void) } EXPORT_SYMBOL(irq_fpu_usable); +#ifdef CONFIG_X86_DEBUG_FPU +DEFINE_PER_CPU(u64, xfd_shadow); +#endif + /* * Save the FPU register state in fpu->state. The register state is * preserved. @@ -99,6 +103,15 @@ EXPORT_SYMBOL(irq_fpu_usable); void save_fpregs_to_fpstate(struct fpu *fpu) { if (likely(use_xsave())) { + /* + * If XFD is armed for an xfeature, XSAVE* will not save + * its state. Verify XFD is clear for all features that + * are in use before XSAVE*. + */ + if (IS_ENABLED(CONFIG_X86_DEBUG_FPU) && xfd_capable() && + boot_cpu_has(X86_FEATURE_XGETBV1)) + WARN_ON_FPU(xgetbv(1) & xfd_debug_shadow()); + os_xsave(&fpu->state->xsave, fpu->state_mask); /* -- 2.17.1
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