From b5c41530ef442dba667c4d964c722e8157f7da72 Mon Sep 17 00:00:00 2001
From: Marcelo Tosatti <mtosatti@redhat.com>
Date: Fri, 11 Mar 2016 16:53:11 +0800
Subject: [PATCH] KVM: x86: move steal time initialization to vcpu entry time
[ Upstream commit 7cae2bedcbd4680b155999655e49c27b9cf020fa ]
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: Sasha Levin <sasha.levin@oracle.com>
---
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 42f1575ab58d9..41a3fb4ed346a 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2117,6 +2117,8 @@ 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;
@@ -2262,12 +2264,6 @@ 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;
@@ -2966,7 +2962,6 @@ 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);
}