diff options
Diffstat (limited to 'arch/x86/kernel/process_64.c')
| -rw-r--r-- | arch/x86/kernel/process_64.c | 28 |
1 files changed, 27 insertions, 1 deletions
diff --git a/arch/x86/kernel/process_64.c b/arch/x86/kernel/process_64.c index d08307df69ad..ec0d836a13b1 100644 --- a/arch/x86/kernel/process_64.c +++ b/arch/x86/kernel/process_64.c @@ -41,6 +41,7 @@ #include <linux/syscalls.h> #include <asm/processor.h> +#include <asm/pkru.h> #include <asm/fpu/internal.h> #include <asm/mmu_context.h> #include <asm/prctl.h> @@ -136,7 +137,7 @@ void __show_regs(struct pt_regs *regs, enum show_regs_mode mode, log_lvl, d3, d6, d7); } - if (boot_cpu_has(X86_FEATURE_OSPKE)) + if (cpu_feature_enabled(X86_FEATURE_OSPKE)) printk("%sPKRU: %08x\n", log_lvl, read_pkru()); } @@ -339,6 +340,29 @@ static __always_inline void load_seg_legacy(unsigned short prev_index, } } +/* + * Store prev's PKRU value and load next's PKRU value if they differ. PKRU + * is not XSTATE managed on context switch because that would require a + * lookup in the task's FPU xsave buffer and require to keep that updated + * in various places. + */ +static __always_inline void x86_pkru_load(struct thread_struct *prev, + struct thread_struct *next) +{ + if (!cpu_feature_enabled(X86_FEATURE_OSPKE)) + return; + + /* Stash the prev task's value: */ + prev->pkru = rdpkru(); + + /* + * PKRU writes are slightly expensive. Avoid them when not + * strictly necessary: + */ + if (prev->pkru != next->pkru) + wrpkru(next->pkru); +} + static __always_inline void x86_fsgsbase_load(struct thread_struct *prev, struct thread_struct *next) { @@ -588,6 +612,8 @@ __switch_to(struct task_struct *prev_p, struct task_struct *next_p) x86_fsgsbase_load(prev, next); + x86_pkru_load(prev, next); + /* * Switch the PDA and FPU contexts. */ |