From: Marcelo Tosatti Date: Wed, 14 Oct 2015 22:33:09 +0000 (-0300) Subject: KVM: x86: move steal time initialization to vcpu entry time X-Git-Tag: v3.10.101~10 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=73c1d981f04cdee52466ea0e5fc0d04c76ad6f49;p=thirdparty%2Fkernel%2Fstable.git KVM: x86: move steal time initialization to vcpu entry time commit 7cae2bedcbd4680b155999655e49c27b9cf020fa upstream. 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: Greg Kroah-Hartman --- diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 41ba726c1ce21..7f2b6dec4b2b1 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1941,6 +1941,8 @@ 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; @@ -2074,12 +2076,6 @@ 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; @@ -2758,7 +2754,6 @@ 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); }