Commit 95443698 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Borislav Petkov
Browse files

x86/fpu: Remove PKRU handling from switch_fpu_finish() 



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

 [ bp: Use cpu_feature_enabled() ]

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Reviewed-by: default avatarBorislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/20210623121456.708180184@linutronix.de
parent 30a304a1

arch/x86/include/asm/fpu/internal.h

+4 −30
Original line number Diff line number Diff line
@@ -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

 * complete FPU state until the return to userland.

 * Delay loading of the complete FPU state until the return to userland.

 * PKRU is handled separately.

 */

static inline void switch_fpu_finish(struct fpu *new_fpu)

{

	u32 pkru_val = init_pkru_value;

	struct pkru_state *pk;



	if (!static_cpu_has(X86_FEATURE_FPU))

		return;



	if (cpu_feature_enabled(X86_FEATURE_FPU))

		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 */