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authorMarcelo Tosatti <mtosatti@redhat.com>2015-10-14 19:33:09 -0300
committerZefan Li <lizefan@huawei.com>2016-03-21 09:17:59 +0800
commit6d470d7cebd87e956e255b242d6c7f4a7d5b62b5 (patch)
treee1e34641c2148f22788d07eb51a977c05269ac85
parent24fa51bde52b3671afa476c96d63bcf8a4e8a307 (diff)
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 <mtosatti@redhat.com> Reviewed-by: David Matlack <dmatlack@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Zefan Li <lizefan@huawei.com>
-rw-r--r--arch/x86/kvm/x86.c9
1 files changed, 2 insertions, 7 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4ad2b7bb382e..9cc83e287adf 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1545,6 +1545,8 @@ 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;
@@ -1665,12 +1667,6 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data)
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;
@@ -2327,7 +2323,6 @@ 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);
}