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Message-Id: <1458643271-4227-135-git-send-email-luis.henriques@canonical.com>
Date: Tue, 22 Mar 2016 10:41:03 +0000
From: Luis Henriques <luis.henriques@...onical.com>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org,
kernel-team@...ts.ubuntu.com
Cc: Marcelo Tosatti <mtosatti@...hat.com>,
Paolo Bonzini <pbonzini@...hat.com>,
Liang Chen <liangchen.linux@...il.com>,
Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 134/142] KVM: x86: move steal time initialization to vcpu entry time
3.16.7-ckt26 -stable review patch. If anyone has any objections, please let me know.
---8<------------------------------------------------------------
From: Marcelo Tosatti <mtosatti@...hat.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@...hat.com>
Reviewed-by: David Matlack <dmatlack@...gle.com>
Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
Cc: Liang Chen <liangchen.linux@...il.com>
Signed-off-by: Luis Henriques <luis.henriques@...onical.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 e9b9fc00da15..89e06ec39dd7 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2025,6 +2025,8 @@ 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;
@@ -2157,12 +2159,6 @@ 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;
@@ -2859,7 +2855,6 @@ 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);
}
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