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Date: Wed, 16 Mar 2016 11:59:29 +0100 From: Jiri Slaby <jslaby@...e.cz> To: stable@...r.kernel.org Cc: linux-kernel@...r.kernel.org, Marcelo Tosatti <mtosatti@...hat.com>, Paolo Bonzini <pbonzini@...hat.com>, Jiri Slaby <jslaby@...e.cz> Subject: [PATCH 3.12 44/58] KVM: x86: move steal time initialization to vcpu entry time From: Marcelo Tosatti <mtosatti@...hat.com> 3.12-stable review patch. If anyone has any objections, please let me know. =============== 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 <mtosatti@...hat.com> Reviewed-by: David Matlack <dmatlack@...gle.com> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com> Signed-off-by: Jiri Slaby <jslaby@...e.cz> --- 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 d3691ab6d6a0..356e78f2ad1a 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1978,6 +1978,8 @@ 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; @@ -2111,12 +2113,6 @@ 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; @@ -2795,7 +2791,6 @@ 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); } -- 2.7.3
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