From: Marcelo Tosatti <mtosatti@redhat.com>
Date: Fri, 29 Jan 2010 19:28:41 +0000 (-0200)
Subject: KVM: PIT: control word is write-only
X-Git-Tag: v2.6.33-rc8~30^2
X-Git-Url: http://ftp.safe.ca/?p=safe%2Fjmp%2Flinux-2.6;a=commitdiff_plain;h=ee73f656a604d5aa9df86a97102e4e462dd79924

KVM: PIT: control word is write-only

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

Cc: stable@kernel.org
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
---

diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
index 296aba4..15578f1 100644
--- a/arch/x86/kvm/i8254.c
+++ b/arch/x86/kvm/i8254.c
@@ -467,6 +467,9 @@ static int pit_ioport_read(struct kvm_io_device *this,
 		return -EOPNOTSUPP;
 
 	addr &= KVM_PIT_CHANNEL_MASK;
+	if (addr == 3)
+		return 0;
+
 	s = &pit_state->channels[addr];
 
 	mutex_lock(&pit_state->lock);