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| author | Marcelo Tosatti <mtosatti@redhat.com> | 2015-03-23 20:21:51 -0300 |
|---|---|---|
| committer | Marcelo Tosatti <mtosatti@redhat.com> | 2015-03-23 20:22:48 -0300 |
| commit | 0a4e6be9ca17c54817cf814b4b5aa60478c6df27 (patch) | |
| tree | 461ed6cace26da5c75d1c01982fde2f3ccc5d4fa /arch/x86/vdso | |
| parent | 58d2930f4ee335ab703d768cb0318331fc1bb62c (diff) | |
| download | linux-0a4e6be9ca17c54817cf814b4b5aa60478c6df27.tar.bz2 | |
x86: kvm: Revert "remove sched notifier for cross-cpu migrations"
The following point:
2. per-CPU pvclock time info is updated if the
underlying CPU changes.
Is not true anymore since "KVM: x86: update pvclock area conditionally,
on cpu migration".
Add task migration notification back.
Problem noticed by Andy Lutomirski.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
CC: stable@kernel.org # 3.11+
Diffstat (limited to 'arch/x86/vdso')
| -rw-r--r-- | arch/x86/vdso/vclock_gettime.c | 16 |
1 files changed, 8 insertions, 8 deletions
diff --git a/arch/x86/vdso/vclock_gettime.c b/arch/x86/vdso/vclock_gettime.c index 9793322751e0..30933760ee5f 100644 --- a/arch/x86/vdso/vclock_gettime.c +++ b/arch/x86/vdso/vclock_gettime.c @@ -82,18 +82,15 @@ static notrace cycle_t vread_pvclock(int *mode) cycle_t ret; u64 last; u32 version; + u32 migrate_count; u8 flags; unsigned cpu, cpu1; /* - * Note: hypervisor must guarantee that: - * 1. cpu ID number maps 1:1 to per-CPU pvclock time info. - * 2. that per-CPU pvclock time info is updated if the - * underlying CPU changes. - * 3. that version is increased whenever underlying CPU - * changes. - * + * When looping to get a consistent (time-info, tsc) pair, we + * also need to deal with the possibility we can switch vcpus, + * so make sure we always re-fetch time-info for the current vcpu. */ do { cpu = __getcpu() & VGETCPU_CPU_MASK; @@ -104,6 +101,8 @@ static notrace cycle_t vread_pvclock(int *mode) pvti = get_pvti(cpu); + migrate_count = pvti->migrate_count; + version = __pvclock_read_cycles(&pvti->pvti, &ret, &flags); /* @@ -115,7 +114,8 @@ static notrace cycle_t vread_pvclock(int *mode) cpu1 = __getcpu() & VGETCPU_CPU_MASK; } while (unlikely(cpu != cpu1 || (pvti->pvti.version & 1) || - pvti->pvti.version != version)); + pvti->pvti.version != version || + pvti->migrate_count != migrate_count)); if (unlikely(!(flags & PVCLOCK_TSC_STABLE_BIT))) *mode = VCLOCK_NONE; |