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x86/fpu: Remove PKRU handling from switch_fpu_finish()

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PKRU is already updated and the xstate is not longer the proper source
of information.

 [ bp: Use cpu_feature_enabled() ]

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov <bp@suse.de>
Reviewed-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121456.708180184@linutronix.de
This commit is contained in:
Thomas Gleixner 2021-06-23 14:02:21 +02:00 committed by Borislav Petkov
parent 30a304a138
commit 954436989c
1 changed files with 4 additions and 30 deletions
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34
arch/x86/include/asm/fpu/internal.h
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@ -523,39 +523,13 @@ static inline void switch_fpu_prepare(struct fpu *old_fpu, int cpu)
*/ */
/* /*
* Load PKRU from the FPU context if available. Delay loading of the * Delay loading of the complete FPU state until the return to userland.
* complete FPU state until the return to userland. * PKRU is handled separately.
*/ */
static inline void switch_fpu_finish(struct fpu *new_fpu) static inline void switch_fpu_finish(struct fpu *new_fpu)
{ {
u32 pkru_val = init_pkru_value; if (cpu_feature_enabled(X86_FEATURE_FPU))
struct pkru_state *pk; set_thread_flag(TIF_NEED_FPU_LOAD);
if (!static_cpu_has(X86_FEATURE_FPU))
return;
set_thread_flag(TIF_NEED_FPU_LOAD);
if (!cpu_feature_enabled(X86_FEATURE_OSPKE))
return;
/*
* PKRU state is switched eagerly because it needs to be valid before we
* return to userland e.g. for a copy_to_user() operation.
*/
if (!(current->flags & PF_KTHREAD)) {
/*
* If the PKRU bit in xsave.header.xfeatures is not set,
* then the PKRU component was in init state, which means
* XRSTOR will set PKRU to 0. If the bit is not set then
* get_xsave_addr() will return NULL because the PKRU value
* in memory is not valid. This means pkru_val has to be
* set to 0 and not to init_pkru_value.
*/
pk = get_xsave_addr(&new_fpu->state.xsave, XFEATURE_PKRU);
pkru_val = pk ? pk->pkru : 0;
}
__write_pkru(pkru_val);
} }
#endif /* _ASM_X86_FPU_INTERNAL_H */ #endif /* _ASM_X86_FPU_INTERNAL_H */