diff options
| author | Marcelo Tosatti <mtosatti@redhat.com> | 2016-11-21 08:50:04 -0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2016-12-22 16:00:56 +0100 |
| commit | 6053a86fe7bd3d5b07b49dae6c05f2cd0d44e687 (patch) | |
| tree | 2719d6b7ef95784f1499ec1ddc66f402129e1ba3 /target/i386/kvm.c | |
| parent | bc20403598702fac96b5a732bdb184ccbe1fcb48 (diff) | |
kvmclock: reduce kvmclock difference on migration
Check for KVM_CAP_ADJUST_CLOCK capability KVM_CLOCK_TSC_STABLE, which
indicates that KVM_GET_CLOCK returns a value as seen by the guest at
that moment.
For new machine types, use this value rather than reading
from guest memory.
This reduces kvmclock difference on migration from 5s to 0.1s
(when max_downtime == 5s).
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Message-Id: <20161121105052.598267440@redhat.com>
[Add comment explaining what is going on. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'target/i386/kvm.c')
| -rw-r--r-- | target/i386/kvm.c | 7 |
1 files changed, 7 insertions, 0 deletions
diff --git a/target/i386/kvm.c b/target/i386/kvm.c index f62264a7a8..10a9cd8f7f 100644 --- a/target/i386/kvm.c +++ b/target/i386/kvm.c @@ -117,6 +117,13 @@ bool kvm_has_smm(void) return kvm_check_extension(kvm_state, KVM_CAP_X86_SMM); } +bool kvm_has_adjust_clock_stable(void) +{ + int ret = kvm_check_extension(kvm_state, KVM_CAP_ADJUST_CLOCK); + + return (ret == KVM_CLOCK_TSC_STABLE); +} + bool kvm_allows_irq0_override(void) { return !kvm_irqchip_in_kernel() || kvm_has_gsi_routing(); |