4.9-stable patches

[thirdparty/kernel/stable-queue.git] / releases / 2.6.32.9 / kvm-pit-control-word-is-write-only.patch

From ee73f656a604d5aa9df86a97102e4e462dd79924 Mon Sep 17 00:00:00 2001
From: Marcelo Tosatti <mtosatti@redhat.com>
Date: Fri, 29 Jan 2010 17:28:41 -0200
Subject: KVM: PIT: control word is write-only

From: Marcelo Tosatti <mtosatti@redhat.com>

commit ee73f656a604d5aa9df86a97102e4e462dd79924 upstream.

PIT control word (address 0x43) is write-only, reads are undefined.

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 arch/x86/kvm/i8254.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -465,6 +465,9 @@ static int pit_ioport_read(struct kvm_io
 		return -EOPNOTSUPP;
 
 	addr &= KVM_PIT_CHANNEL_MASK;
+	if (addr == 3)
+		return 0;
+
 	s = &pit_state->channels[addr];
 
 	mutex_lock(&pit_state->lock);