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Commit 7cae2bed authored by Marcelo Tosatti's avatar Marcelo Tosatti Committed by Paolo Bonzini
Browse files

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

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: default avatarMarcelo Tosatti <mtosatti@redhat.com>
Reviewed-by: default avatarDavid Matlack <dmatlack@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 5225fdf8

arch/x86/kvm/x86.c

+2 −7
Original line number Original line Diff line number Diff line
@@ -1903,6 +1903,8 @@ static void accumulate_steal_time(struct kvm_vcpu *vcpu) 




static void record_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))

	if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED))

		return;

		return;
@@ -2053,12 +2055,6 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) 
		if (!(data & KVM_MSR_ENABLED))

		if (!(data & KVM_MSR_ENABLED))

			break;

			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);

		kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);





		break;

		break;
@@ -2634,7 +2630,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) 
		vcpu->cpu = cpu;

		vcpu->cpu = cpu;

	}

	}





	accumulate_steal_time(vcpu);

	kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);

	kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);

}

}