[ 3.5.y.z extended stable ] Patch "KVM: VMX: fix halt emulation while emulating invalid guest" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    KVM: VMX: fix halt emulation while emulating invalid guest

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 40bb19b71ff8729b2caf7fbe76c71b2afb657d1d Mon Sep 17 00:00:00 2001
From: Gleb Natapov <gleb at redhat.com>
Date: Wed, 8 May 2013 18:38:44 +0300
Subject: [PATCH] KVM: VMX: fix halt emulation while emulating invalid guest
 sate

commit 8d76c49e9ffeee839bc0b7a3278a23f99101263e upstream.

The invalid guest state emulation loop does not check halt_request
which causes 100% cpu loop while guest is in halt and in invalid
state, but more serious issue is that this leaves halt_request set, so
random instruction emulated by vm86 #GP exit can be interpreted
as halt which causes guest hang. Fix both problems by handling
halt_request in emulation loop.

Reported-by: Tomas Papan <tomas.papan at gmail.com>
Tested-by: Tomas Papan <tomas.papan at gmail.com>
Reviewed-by: Paolo Bonzini <pbonzini at redhat.com>
Signed-off-by: Gleb Natapov <gleb at redhat.com>
[ luis: adjust context ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 arch/x86/kvm/vmx.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 61593fd..eed06fc 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -4920,6 +4920,12 @@ static int handle_invalid_guest_state(struct kvm_vcpu *vcpu)
 		if (err != EMULATE_DONE)
 			return 0;

+		if (vcpu->arch.halt_request) {
+			vcpu->arch.halt_request = 0;
+			ret = kvm_emulate_halt(vcpu);
+			goto out;
+		}
+
 		if (signal_pending(current))
 			goto out;
 		if (need_resched())
--
1.8.1.2