From 4e87173eacfd0d798aeeba14026893797826bc93 Mon Sep 17 00:00:00 2001 From: Glauber de Oliveira Costa Date: Wed, 30 Jan 2008 13:31:03 +0100 Subject: [PATCH] x86: split get_cycles_sync This patch splits get_cycles_sync() into __get_cycles_sync(), and the rdtscll part. Paravirt guests cannot issue rdtscl directly, as it involves a function call in vdso area. So, using the __get_cycles_sync() base, we introduce vget_cycles_sync, which then calls the native version of rdtscll. Ideally, however, a guest should define its own clocksource, together with a vread function Signed-off-by: Glauber de Oliveira Costa Signed-off-by: Ingo Molnar Signed-off-by: Thomas Gleixner --- arch/x86/kernel/tsc_64.c | 2 +- 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 204a908..3723401 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 d7b1c4e..9b7d264 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); -- 2.7.4