From 72a6c08c44e4460e39315ca828f60b8d5afd6b19 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 23 Jun 2021 14:02:23 +0200 Subject: x86/pkru: Remove xstate fiddling from write_pkru() The PKRU value of a task is stored in task->thread.pkru when the task is scheduled out. PKRU is restored on schedule in from there. So keeping the XSAVE buffer up to date is a pointless exercise. Remove the xstate fiddling and cleanup all related functions. Signed-off-by: Thomas Gleixner Signed-off-by: Borislav Petkov Reviewed-by: Borislav Petkov Link: https://lkml.kernel.org/r/20210623121456.897372712@linutronix.de --- arch/x86/include/asm/pkru.h | 17 ++++------------- arch/x86/include/asm/special_insns.h | 14 +------------- 2 files changed, 5 insertions(+), 26 deletions(-) (limited to 'arch/x86/include') diff --git a/arch/x86/include/asm/pkru.h b/arch/x86/include/asm/pkru.h index 7e4550911c51..ccc539faa5bb 100644 --- a/arch/x86/include/asm/pkru.h +++ b/arch/x86/include/asm/pkru.h @@ -41,23 +41,14 @@ static inline u32 read_pkru(void) static inline void write_pkru(u32 pkru) { - struct pkru_state *pk; - if (!cpu_feature_enabled(X86_FEATURE_OSPKE)) return; - - pk = get_xsave_addr(¤t->thread.fpu.state.xsave, XFEATURE_PKRU); - /* - * The PKRU value in xstate needs to be in sync with the value that is - * written to the CPU. The FPU restore on return to userland would - * otherwise load the previous value again. + * WRPKRU is relatively expensive compared to RDPKRU. + * Avoid WRPKRU when it would not change the value. */ - fpregs_lock(); - if (pk) - pk->pkru = pkru; - __write_pkru(pkru); - fpregs_unlock(); + if (pkru != rdpkru()) + wrpkru(pkru); } static inline void pkru_write_default(void) diff --git a/arch/x86/include/asm/special_insns.h b/arch/x86/include/asm/special_insns.h index 2acd6cb62328..f3fbb84ff8a7 100644 --- a/arch/x86/include/asm/special_insns.h +++ b/arch/x86/include/asm/special_insns.h @@ -104,25 +104,13 @@ static inline void wrpkru(u32 pkru) : : "a" (pkru), "c"(ecx), "d"(edx)); } -static inline void __write_pkru(u32 pkru) -{ - /* - * WRPKRU is relatively expensive compared to RDPKRU. - * Avoid WRPKRU when it would not change the value. - */ - if (pkru == rdpkru()) - return; - - wrpkru(pkru); -} - #else static inline u32 rdpkru(void) { return 0; } -static inline void __write_pkru(u32 pkru) +static inline void wrpkru(u32 pkru) { } #endif -- cgit v1.2.3