KVM: PPC: Fix a mmio_host_swabbed uninitialized usage issue

When KVM emulates VMX store, it will invoke kvmppc_get_vmx_data() to
retrieve VMX reg val. kvmppc_get_vmx_data() will check mmio_host_swabbed
to decide which double word of vr[] to be used. But the
mmio_host_swabbed can be uninitialized during VMX store procedure:

kvmppc_emulate_loadstore
	\- kvmppc_handle_store128_by2x64
		\- kvmppc_get_vmx_data

So vcpu->arch.mmio_host_swabbed is not meant to be used at all for
emulation of store instructions, and this patch makes that true for
VMX stores. This patch also initializes mmio_host_swabbed to avoid
possible future problems.

Signed-off-by: Simon Guo <[email protected]>
Signed-off-by: Paul Mackerras <[email protected]>

Author: justdoitqd

arch/powerpc/kvm/emulate_loadstore.c

@@ -111,6 +111,7 @@ int kvmppc_emulate_loadstore(struct kvm_vcpu *vcpu)
 	vcpu->arch.mmio_sp64_extend = 0;
 	vcpu->arch.mmio_sign_extend = 0;
 	vcpu->arch.mmio_vmx_copy_nums = 0;
+	vcpu->arch.mmio_host_swabbed = 0;
 
 	switch (get_op(inst)) {
 	case 31:

arch/powerpc/kvm/powerpc.c

@@ -1374,7 +1374,7 @@ static inline int kvmppc_get_vmx_data(struct kvm_vcpu *vcpu, int rs, u64 *val)
 	if (di > 1)
 		return -1;
 
-	if (vcpu->arch.mmio_host_swabbed)
+	if (kvmppc_need_byteswap(vcpu))
 		di = 1 - di;
 
 	w0 = vrs.u[di * 2];