linux/arch/x86/include/asm/pvclock-abi.h
Marcelo Tosatti 611917258f x86: kvmclock: add flag to indicate pvclock counts from zero
Setting sched clock stable for kvmclock causes the printk timestamps
to not start from zero, which is different from baremetal and
can possibly break userspace. Add a flag to indicate that
hypervisor sets clock base at zero when kvmclock is initialized.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2015-05-29 14:01:39 +02:00

47 lines
1.4 KiB
C

#ifndef _ASM_X86_PVCLOCK_ABI_H
#define _ASM_X86_PVCLOCK_ABI_H
#ifndef __ASSEMBLY__
/*
* These structs MUST NOT be changed.
* They are the ABI between hypervisor and guest OS.
* Both Xen and KVM are using this.
*
* pvclock_vcpu_time_info holds the system time and the tsc timestamp
* of the last update. So the guest can use the tsc delta to get a
* more precise system time. There is one per virtual cpu.
*
* pvclock_wall_clock references the point in time when the system
* time was zero (usually boot time), thus the guest calculates the
* current wall clock by adding the system time.
*
* 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.
*/
struct pvclock_vcpu_time_info {
u32 version;
u32 pad0;
u64 tsc_timestamp;
u64 system_time;
u32 tsc_to_system_mul;
s8 tsc_shift;
u8 flags;
u8 pad[2];
} __attribute__((__packed__)); /* 32 bytes */
struct pvclock_wall_clock {
u32 version;
u32 sec;
u32 nsec;
} __attribute__((__packed__));
#define PVCLOCK_TSC_STABLE_BIT (1 << 0)
#define PVCLOCK_GUEST_STOPPED (1 << 1)
#define PVCLOCK_COUNTS_FROM_ZERO (1 << 2)
#endif /* __ASSEMBLY__ */
#endif /* _ASM_X86_PVCLOCK_ABI_H */