Commit 3d29c6db authored by Marcelo Tosatti's avatar Marcelo Tosatti Committed by Luis Henriques

KVM: x86: move steal time initialization to vcpu entry time

commit 7cae2bed 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: default avatarMarcelo Tosatti <mtosatti@redhat.com>
Reviewed-by: default avatarDavid Matlack <dmatlack@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Cc: Liang Chen <liangchen.linux@gmail.com>
Signed-off-by: default avatarLuis Henriques <luis.henriques@canonical.com>
parent 9541db7a
...@@ -2025,6 +2025,8 @@ static void accumulate_steal_time(struct kvm_vcpu *vcpu) ...@@ -2025,6 +2025,8 @@ static void accumulate_steal_time(struct kvm_vcpu *vcpu)
static void record_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)) if (!(vcpu->arch.st.msr_val & KVM_MSR_ENABLED))
return; return;
...@@ -2157,12 +2159,6 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) ...@@ -2157,12 +2159,6 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
if (!(data & KVM_MSR_ENABLED)) if (!(data & KVM_MSR_ENABLED))
break; 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); kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);
break; break;
...@@ -2859,7 +2855,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) ...@@ -2859,7 +2855,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
vcpu->cpu = cpu; vcpu->cpu = cpu;
} }
accumulate_steal_time(vcpu);
kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu); kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);
} }
......
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