diff options
| -rw-r--r-- | arch/x86/include/asm/special_insns.h | 6 | ||||
| -rw-r--r-- | arch/x86/include/asm/sync_core.h | 26 |
2 files changed, 24 insertions, 8 deletions
diff --git a/arch/x86/include/asm/special_insns.h b/arch/x86/include/asm/special_insns.h index 59a3e13204c3..5999b0b3dd4a 100644 --- a/arch/x86/include/asm/special_insns.h +++ b/arch/x86/include/asm/special_insns.h @@ -234,6 +234,12 @@ static inline void clwb(volatile void *__p) #define nop() asm volatile ("nop") +static inline void serialize(void) +{ + /* Instruction opcode for SERIALIZE; supported in binutils >= 2.35. */ + asm volatile(".byte 0xf, 0x1, 0xe8" ::: "memory"); +} + #endif /* __KERNEL__ */ #endif /* _ASM_X86_SPECIAL_INSNS_H */ diff --git a/arch/x86/include/asm/sync_core.h b/arch/x86/include/asm/sync_core.h index fdb5b356e59b..4631c0f969d4 100644 --- a/arch/x86/include/asm/sync_core.h +++ b/arch/x86/include/asm/sync_core.h @@ -5,6 +5,7 @@ #include <linux/preempt.h> #include <asm/processor.h> #include <asm/cpufeature.h> +#include <asm/special_insns.h> #ifdef CONFIG_X86_32 static inline void iret_to_self(void) @@ -54,14 +55,23 @@ static inline void iret_to_self(void) static inline void sync_core(void) { /* - * There are quite a few ways to do this. IRET-to-self is nice - * because it works on every CPU, at any CPL (so it's compatible - * with paravirtualization), and it never exits to a hypervisor. - * The only down sides are that it's a bit slow (it seems to be - * a bit more than 2x slower than the fastest options) and that - * it unmasks NMIs. The "push %cs" is needed because, in - * paravirtual environments, __KERNEL_CS may not be a valid CS - * value when we do IRET directly. + * The SERIALIZE instruction is the most straightforward way to + * do this but it not universally available. + */ + if (static_cpu_has(X86_FEATURE_SERIALIZE)) { + serialize(); + return; + } + + /* + * For all other processors, there are quite a few ways to do this. + * IRET-to-self is nice because it works on every CPU, at any CPL + * (so it's compatible with paravirtualization), and it never exits + * to a hypervisor. The only down sides are that it's a bit slow + * (it seems to be a bit more than 2x slower than the fastest + * options) and that it unmasks NMIs. The "push %cs" is needed + * because, in paravirtual environments, __KERNEL_CS may not be a + * valid CS value when we do IRET directly. * * In case NMI unmasking or performance ever becomes a problem, * the next best option appears to be MOV-to-CR2 and an |