From b5c41530ef442dba667c4d964c722e8157f7da72 Mon Sep 17 00:00:00 2001 From: Marcelo Tosatti Date: Fri, 11 Mar 2016 16:53:11 +0800 Subject: [PATCH] KVM: x86: move steal time initialization to vcpu entry time [ Upstream commit 7cae2bedcbd4680b155999655e49c27b9cf020fa ] 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 Reviewed-by: David Matlack Signed-off-by: Paolo Bonzini Signed-off-by: Sasha Levin --- arch/x86/kvm/x86.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-) diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 42f1575..41a3fb4 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -2117,6 +2117,8 @@ 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; @@ -2262,12 +2264,6 @@ 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; @@ -2966,7 +2962,6 @@ 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); } -- 2.7.4