From 35f3fae17849793c7c031b00ec972f3d9057744b Mon Sep 17 00:00:00 2001 From: Wanpeng Li Date: Tue, 3 May 2016 11:43:10 +0800 Subject: [PATCH] kvm: robustify steal time record MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Signed-off-by: Wanpeng Li Signed-off-by: Radim Krčmář --- arch/x86/kvm/x86.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 96e81d284deb..57a62d1e2f5d 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -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)); -- 2.20.1