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author | Glauber de Oliveira Costa <gcosta@redhat.com> | 2008-01-30 13:31:03 +0100 |
---|---|---|
committer | Ingo Molnar <mingo@elte.hu> | 2008-01-30 13:31:03 +0100 |
commit | 4e87173eacfd0d798aeeba14026893797826bc93 (patch) | |
tree | 14a47677f3cc7074a5b190e159873b925c8deb77 /include/asm-x86/tsc.h | |
parent | x86: allow sched clock to be overridden by paravirt (diff) | |
download | linux-4e87173eacfd0d798aeeba14026893797826bc93.tar.xz linux-4e87173eacfd0d798aeeba14026893797826bc93.zip |
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 <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'include/asm-x86/tsc.h')
-rw-r--r-- | include/asm-x86/tsc.h | 37 |
1 files changed, 33 insertions, 4 deletions
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); |