Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 3.10 09/18] KVM: x86: move steal time initialization to vcpu entry time | Date | Mon, 14 Mar 2016 10:53:07 -0700 |
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3.10-stable review patch. If anyone has any objections, please let me know.
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From: Marcelo Tosatti <mtosatti@redhat.com>
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@redhat.com> Reviewed-by: David Matlack <dmatlack@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- arch/x86/kvm/x86.c | 9 ++------- 1 file changed, 2 insertions(+), 7 deletions(-)
--- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1941,6 +1941,8 @@ static void accumulate_steal_time(struct 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 * 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->cpu = cpu; } - accumulate_steal_time(vcpu); kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu); }
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