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@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

diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h
index 2a484f5..528a868 100644 (file)
--- 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 */