linux/arch/x86/include/asm/pvclock.h
Minfei Huang 749d088b8e pvclock: Add CPU barriers to get correct version value
Protocol for the "version" fields is: hypervisor raises it (making it
uneven) before it starts updating the fields and raises it again (making
it even) when it is done.  Thus the guest can make sure the time values
it got are consistent by checking the version before and after reading
them.

Add CPU barries after getting version value just like what function
vread_pvclock does, because all of callees in this function is inline.

Fixes: 502dfeff23
Cc: stable@vger.kernel.org
Signed-off-by: Minfei Huang <mnghuan@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-06-27 15:12:14 +02:00

107 lines
2.5 KiB
C

#ifndef _ASM_X86_PVCLOCK_H
#define _ASM_X86_PVCLOCK_H
#include <linux/clocksource.h>
#include <asm/pvclock-abi.h>
#ifdef CONFIG_KVM_GUEST
extern struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void);
#else
static inline struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void)
{
return NULL;
}
#endif
/* some helper functions for xen and kvm pv clock sources */
cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src);
u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src);
void pvclock_set_flags(u8 flags);
unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src);
void pvclock_read_wallclock(struct pvclock_wall_clock *wall,
struct pvclock_vcpu_time_info *vcpu,
struct timespec *ts);
void pvclock_resume(void);
void pvclock_touch_watchdogs(void);
/*
* Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction,
* yielding a 64-bit result.
*/
static inline u64 pvclock_scale_delta(u64 delta, u32 mul_frac, int shift)
{
u64 product;
#ifdef __i386__
u32 tmp1, tmp2;
#else
ulong tmp;
#endif
if (shift < 0)
delta >>= -shift;
else
delta <<= shift;
#ifdef __i386__
__asm__ (
"mul %5 ; "
"mov %4,%%eax ; "
"mov %%edx,%4 ; "
"mul %5 ; "
"xor %5,%5 ; "
"add %4,%%eax ; "
"adc %5,%%edx ; "
: "=A" (product), "=r" (tmp1), "=r" (tmp2)
: "a" ((u32)delta), "1" ((u32)(delta >> 32)), "2" (mul_frac) );
#elif defined(__x86_64__)
__asm__ (
"mulq %[mul_frac] ; shrd $32, %[hi], %[lo]"
: [lo]"=a"(product),
[hi]"=d"(tmp)
: "0"(delta),
[mul_frac]"rm"((u64)mul_frac));
#else
#error implement me!
#endif
return product;
}
static __always_inline
u64 pvclock_get_nsec_offset(const struct pvclock_vcpu_time_info *src)
{
u64 delta = rdtsc_ordered() - src->tsc_timestamp;
return pvclock_scale_delta(delta, src->tsc_to_system_mul,
src->tsc_shift);
}
static __always_inline
unsigned __pvclock_read_cycles(const struct pvclock_vcpu_time_info *src,
cycle_t *cycles, u8 *flags)
{
unsigned version;
cycle_t ret, offset;
u8 ret_flags;
version = src->version;
/* Make the latest version visible */
smp_rmb();
offset = pvclock_get_nsec_offset(src);
ret = src->system_time + offset;
ret_flags = src->flags;
*cycles = ret;
*flags = ret_flags;
return version;
}
struct pvclock_vsyscall_time_info {
struct pvclock_vcpu_time_info pvti;
} __attribute__((__aligned__(SMP_CACHE_BYTES)));
#define PVTI_SIZE sizeof(struct pvclock_vsyscall_time_info)
#endif /* _ASM_X86_PVCLOCK_H */