KVM: ia64: fix zero extending for mmio ld1/2/4 emulation in KVM

Only copy in the data actually requested by the instruction emulation
and zero pad the destination register first. This avoids the problem
where emulated mmio access got garbled data from ld2.acq instructions
in the vga console driver.
Signed-off-by: NJes Sorensen <jes@sgi.com>
Acked-by: NXiantao Zhang <xiantao.zhang@intel.com>
Signed-off-by: NAvi Kivity <avi@qumranet.com>

arch/ia64/kvm/mmio.c

@@ -159,7 +159,8 @@ static void mmio_access(struct kvm_vcpu *vcpu, u64 src_pa, u64 *dest,
 
 	if (p->u.ioreq.state == STATE_IORESP_READY) {
 		if (dir == IOREQ_READ)
-			*dest = p->u.ioreq.data;
+			/* it's necessary to ensure zero extending */
+			*dest = p->u.ioreq.data & (~0UL >> (64-(s*8)));
 	} else
 		panic_vm(vcpu);
 out: