linux-kernel - [PATCH 076/115] KVM: VMX: fix halt emulation while emulating invalid guest sate

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Date:	Mon, 20 May 2013 11:51:16 +0100
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Gleb Natapov <gleb@...hat.com>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 076/115] KVM: VMX: fix halt emulation while emulating invalid guest sate

3.5.7.13 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Gleb Natapov <gleb@...hat.com>

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@...il.com>
Tested-by: Tomas Papan <tomas.papan@...il.com>
Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>
Signed-off-by: Gleb Natapov <gleb@...hat.com>
[ luis: adjust context ]
Signed-off-by: Luis Henriques <luis.henriques@...onical.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

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