KVM: x86: move steal time initialization to vcpu entry time (7cae2bed) · Commits · 戴 / test

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>

arch/x86/kvm/x86.c

+2 −7

Original line number	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)
		{
		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);
		}

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