This is a note to let you know that I've just added the patch titled
KVM: x86: move steal time initialization to vcpu entry time
to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
kvm-x86-move-steal-time-initialization-to-vcpu-entry-time.patch
and it can be found in the queue-3.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 7cae2bedcbd4680b155999655e49c27b9cf020fa Mon Sep 17 00:00:00 2001
From: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Date: Wed, 14 Oct 2015 19:33:09 -0300
Subject: KVM: x86: move steal time initialization to vcpu entry time
From: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
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@xxxxxxxxxx>
Reviewed-by: David Matlack <dmatlack@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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
@@ -1991,6 +1991,8 @@ 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;
@@ -2123,12 +2125,6 @@ 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;
@@ -2818,7 +2814,6 @@ void kvm_arch_vcpu_load(struct kvm_vcpu
vcpu->cpu = cpu;
}
- accumulate_steal_time(vcpu);
kvm_make_request(KVM_REQ_STEAL_UPDATE, vcpu);
}
Patches currently in stable-queue which might be from mtosatti@xxxxxxxxxx are
queue-3.14/kvm-x86-move-steal-time-initialization-to-vcpu-entry-time.patch
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