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KVM: x86: update pvclock area conditionally, on cpu migration

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As requested by Glauber, do not update kvmclock area on vcpu->pcpu
migration, in case the host has stable TSC.

This is to reduce cacheline bouncing.

Acked-by: Glauber Costa <glommer@parallels.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
This commit is contained in:
Marcelo Tosatti 2012-11-27 23:29:04 -02:00
parent b48aa97e38
commit d98d07ca7e
1 changed files with 6 additions and 1 deletions
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7
arch/x86/kvm/x86.c
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@ -2627,7 +2627,12 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
kvm_x86_ops->write_tsc_offset(vcpu, offset);
vcpu->arch.tsc_catchup = 1;
}
kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
/*
* On a host with synchronized TSC, there is no need to update
* kvmclock on vcpu->cpu migration
*/
if (!vcpu->kvm->arch.use_master_clock || vcpu->cpu == -1)
kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
if (vcpu->cpu != cpu)
kvm_migrate_timers(vcpu);
vcpu->cpu = cpu;