[patch V2 49/52] x86/fpu: Remove PKRU handling from switch_fpu_finish()

Thomas Gleixner
2021-06-14T16:40:50Z

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

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
arch/x86/include/asm/fpu/internal.h | 34 ++++------------------------------
1 file changed, 4 insertions(+), 30 deletions(-)

--- a/arch/x86/include/asm/fpu/internal.h
+++ b/arch/x86/include/asm/fpu/internal.h
@@ -517,39 +517,13 @@ static inline void switch_fpu_prepare(st
*/

/*
- * 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 seperately.
*/
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 (static_cpu_has(X86_FEATURE_FPU))
+ set_thread_flag(TIF_NEED_FPU_LOAD);
}

#endif /* _ASM_X86_FPU_INTERNAL_H */