linux-kernel - [23/94] KVM: VMX: fix halt emulation while emulating invalid guest sate

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Date:	Tue, 28 May 2013 04:49:53 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "Gleb Natapov" <gleb@...hat.com>,
	"Paolo Bonzini" <pbonzini@...hat.com>,
	"Tomas Papan" <tomas.papan@...il.com>
Subject: [23/94] KVM: VMX: fix halt emulation while emulating invalid
 guest sate

3.2.46-rc1 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>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 arch/x86/kvm/vmx.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -4882,6 +4882,12 @@ static int handle_invalid_guest_state(st
 		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())

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