diff options
Diffstat (limited to 'arch/x86/include/asm/sync_core.h')
-rw-r--r-- | arch/x86/include/asm/sync_core.h | 34 |
1 files changed, 22 insertions, 12 deletions
diff --git a/arch/x86/include/asm/sync_core.h b/arch/x86/include/asm/sync_core.h index fdb5b356e59b..0fd4a9dfb29c 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) @@ -46,22 +47,34 @@ static inline void iret_to_self(void) * * b) Text was modified on a different CPU, may subsequently be * executed on this CPU, and you want to make sure the new version - * gets executed. This generally means you're calling this in a IPI. + * gets executed. This generally means you're calling this in an IPI. * * If you're calling this for a different reason, you're probably doing * it wrong. + * + * Like all of Linux's memory ordering operations, this is a + * compiler barrier as well. */ 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 is 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 downsides 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 @@ -71,9 +84,6 @@ static inline void sync_core(void) * CPUID is the conventional way, but it's nasty: it doesn't * exist on some 486-like CPUs, and it usually exits to a * hypervisor. - * - * Like all of Linux's memory ordering operations, this is a - * compiler barrier as well. */ iret_to_self(); } |