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KVM: x86: move steal time initialization to vcpu entry time

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As reported at https://bugs.launchpad.net/qemu/+bug/1494350,
it is possible to have vcpu->arch.st.last_steal initialized
from a thread other than vcpu thread, say the iothread, via
KVM_SET_MSRS.

Which can cause an overflow later (when subtracting from vcpu threads
sched_info.run_delay).

To avoid that, move steal time accumulation to vcpu entry time,
before copying steal time data to guest.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Reviewed-by: David Matlack <dmatlack@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Marcelo Tosatti 2015-10-14 19:33:09 -03:00 committed by Paolo Bonzini
parent 5225fdf8c8
commit 7cae2bedcb
1 changed files with 2 additions and 7 deletions
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9
arch/x86/kvm/x86.c
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@ -1903,6 +1903,8 @@ static void accumulate_steal_time(struct kvm_vcpu *vcpu)
static void record_steal_time(struct kvm_vcpu *vcpu)
{
accumulate_steal_time(vcpu);
if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED))
return;
@ -2053,12 +2055,6 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
if (!(data & KVM_MSR_ENABLED))
break;
vcpu->arch.st.last_steal = current->sched_info.run_delay;
preempt_disable();
accumulate_steal_time(vcpu);
preempt_enable();
kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);
break;
@ -2634,7 +2630,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
vcpu->cpu = cpu;
}
accumulate_steal_time(vcpu);
kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);
}