[tip: x86/fpu] x86/fpu: Remove PKRU handling from switch_fpu_finish()

[tip-bot2 for Thomas Gleixner]

The following commit has been merged into the x86/fpu branch of tip:

Commit-ID:     954436989cc550dd91aab98363240c9c0a4b7e23
Gitweb:        https://git.kernel.org/tip/954436989cc550dd91aab98363240c9c0a4b7e23
Author:        Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate:    Wed, 23 Jun 2021 14:02:21 +02:00
Committer:     Borislav Petkov <bp@xxxxxxx>
CommitterDate: Wed, 23 Jun 2021 19:54:49 +02:00

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: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Reviewed-by: Borislav Petkov <bp@xxxxxxx>
Link: https://lkml.kernel.org/r/20210623121456.708180184@xxxxxxxxxxxxx
---
 arch/x86/include/asm/fpu/internal.h | 34 +++-------------------------
 1 file changed, 4 insertions(+), 30 deletions(-)

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 2a484f5..528a868 100644
--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -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;
-
-	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);
+	if (cpu_feature_enabled(X86_FEATURE_FPU))
+		set_thread_flag(TIF_NEED_FPU_LOAD);
 }
 
 #endif /* _ASM_X86_FPU_INTERNAL_H */