kvm: robustify steal time record (35f3fae1) · Commits · 戴 / test

Guest should only trust data to be valid when version haven't changed before and after reads of steal time. Besides not changing, it has to be an even number. Hypervisor may write an odd number to version field to indicate that an update is in progress. kvm_steal_clock() in guest has already done the read side, make write side in hypervisor more robust by following the above rule. Reviewed-by:

Wincy Van <fanwenyi0529@gmail.com> Signed-off-by:

Wanpeng Li <wanpeng.li@hotmail.com> Signed-off-by:

Radim Krčmář <rkrcmar@redhat.com>

arch/x86/kvm/x86.c

+17 −1

Original line number	Diff line number	Diff line
		@@ -2011,10 +2011,26 @@ static void record_steal_time(struct kvm_vcpu *vcpu)
		&vcpu->arch.st.steal, sizeof(struct kvm_steal_time))))
		return;

		if (vcpu->arch.st.steal.version & 1)
		vcpu->arch.st.steal.version += 1; /* first time write, random junk */

		vcpu->arch.st.steal.version += 1;

		kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.st.stime,
		&vcpu->arch.st.steal, sizeof(struct kvm_steal_time));

		smp_wmb();

		vcpu->arch.st.steal.steal += current->sched_info.run_delay -
		vcpu->arch.st.last_steal;
		vcpu->arch.st.last_steal = current->sched_info.run_delay;
		vcpu->arch.st.steal.version += 2;

		kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.st.stime,
		&vcpu->arch.st.steal, sizeof(struct kvm_steal_time));

		smp_wmb();

		vcpu->arch.st.steal.version += 1;

		kvm_write_guest_cached(vcpu->kvm, &vcpu->arch.st.stime,
		&vcpu->arch.st.steal, sizeof(struct kvm_steal_time));

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