commit 336f40a728b9a4a5db5e1df5c89852c79ff95604
Author: Marcelo Tosatti <mtosatti@redhat.com>
Date:   Fri Jan 29 17:28:41 2010 -0200

    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 caad189..6a74246 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);