diff options
| -rw-r--r-- | arch/x86/kernel/tsc_64.c | 2 | ||||
| -rw-r--r-- | include/asm-x86/tsc.h | 37 |
2 files changed, 34 insertions, 5 deletions
diff --git a/arch/x86/kernel/tsc_64.c b/arch/x86/kernel/tsc_64.c index 204a9080af04..3723401c4593 100644 --- a/arch/x86/kernel/tsc_64.c +++ b/arch/x86/kernel/tsc_64.c @@ -306,7 +306,7 @@ static cycle_t read_tsc(void) static cycle_t __vsyscall_fn vread_tsc(void) { - cycle_t ret = (cycle_t)get_cycles_sync(); + cycle_t ret = (cycle_t)vget_cycles_sync(); return ret; } diff --git a/include/asm-x86/tsc.h b/include/asm-x86/tsc.h index d7b1c4e7a108..9b7d264897fa 100644 --- a/include/asm-x86/tsc.h +++ b/include/asm-x86/tsc.h @@ -33,14 +33,14 @@ static inline cycles_t get_cycles(void) } /* Like get_cycles, but make sure the CPU is synchronized. */ -static __always_inline cycles_t get_cycles_sync(void) +static __always_inline cycles_t __get_cycles_sync(void) { unsigned long long ret; unsigned eax, edx; /* - * Use RDTSCP if possible; it is guaranteed to be synchronous - * and doesn't cause a VMEXIT on Hypervisors + * Use RDTSCP if possible; it is guaranteed to be synchronous + * and doesn't cause a VMEXIT on Hypervisors */ alternative_io(ASM_NOP3, ".byte 0x0f,0x01,0xf9", X86_FEATURE_RDTSCP, ASM_OUTPUT2("=a" (eax), "=d" (edx)), @@ -55,11 +55,40 @@ static __always_inline cycles_t get_cycles_sync(void) */ alternative_io("cpuid", ASM_NOP2, X86_FEATURE_SYNC_RDTSC, "=a" (eax), "0" (1) : "ebx","ecx","edx","memory"); - rdtscll(ret); + return 0; +} + +static __always_inline cycles_t get_cycles_sync(void) +{ + unsigned long long ret; + ret = __get_cycles_sync(); + if (!ret) + rdtscll(ret); return ret; } +#ifdef CONFIG_PARAVIRT +/* + * For paravirt guests, some functionalities are executed through function + * pointers in the various pvops structures. + * These function pointers exist inside the kernel and can not + * be accessed by user space. To avoid this, we make a copy of the + * get_cycles_sync (called in kernel) but force the use of native_read_tsc. + * Ideally, the guest should set up it's own clock and vread + */ +static __always_inline long long vget_cycles_sync(void) +{ + unsigned long long ret; + ret = __get_cycles_sync(); + if (!ret) + ret = native_read_tsc(); + return ret; +} +#else +# define vget_cycles_sync() get_cycles_sync() +#endif + extern void tsc_init(void); extern void mark_tsc_unstable(char *reason); extern int unsynchronized_tsc(void); |