KVM: PPC: Fix emulated MMIO sign-extension

When the guest does a sign-extending load instruction (such as lha
or lwa) to an emulated MMIO location, it results in a call to
kvmppc_handle_loads() in the host.  That function sets the
vcpu->arch.mmio_sign_extend flag and calls kvmppc_handle_load()
to do the rest of the work.  However, kvmppc_handle_load() sets
the mmio_sign_extend flag to 0 unconditionally, so the sign
extension never gets done.

To fix this, we rename kvmppc_handle_load to __kvmppc_handle_load
and add an explicit parameter to indicate whether sign extension
is required.  kvmppc_handle_load() and kvmppc_handle_loads() then
become 1-line functions that just call __kvmppc_handle_load()
with the extra parameter.

Reported-by: Bin Lu <lblulb@linux.vnet.ibm.com>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/kvm/powerpc.c

@@ -800,9 +800,9 @@ static void kvmppc_complete_mmio_load(struct kvm_vcpu *vcpu,
 	}
 }
 
-int kvmppc_handle_load(struct kvm_run *run, struct kvm_vcpu *vcpu,
-		       unsigned int rt, unsigned int bytes,
-		       int is_default_endian)
+static int __kvmppc_handle_load(struct kvm_run *run, struct kvm_vcpu *vcpu,
+				unsigned int rt, unsigned int bytes,
+				int is_default_endian, int sign_extend)
 {
 	int idx, ret;
 	bool host_swabbed;
@@ -827,7 +827,7 @@ int kvmppc_handle_load(struct kvm_run *run, struct kvm_vcpu *vcpu,
 	vcpu->arch.mmio_host_swabbed = host_swabbed;
 	vcpu->mmio_needed = 1;
 	vcpu->mmio_is_write = 0;
-	vcpu->arch.mmio_sign_extend = 0;
+	vcpu->arch.mmio_sign_extend = sign_extend;
 
 	idx = srcu_read_lock(&vcpu->kvm->srcu);
 
@@ -844,6 +844,13 @@ int kvmppc_handle_load(struct kvm_run *run, struct kvm_vcpu *vcpu,
 
 	return EMULATE_DO_MMIO;
 }
+
+int kvmppc_handle_load(struct kvm_run *run, struct kvm_vcpu *vcpu,
+		       unsigned int rt, unsigned int bytes,
+		       int is_default_endian)
+{
+	return __kvmppc_handle_load(run, vcpu, rt, bytes, is_default_endian, 0);
+}
 EXPORT_SYMBOL_GPL(kvmppc_handle_load);
 
 /* Same as above, but sign extends */
@@ -851,12 +858,7 @@ int kvmppc_handle_loads(struct kvm_run *run, struct kvm_vcpu *vcpu,
 			unsigned int rt, unsigned int bytes,
 			int is_default_endian)
 {
-	int r;
-
-	vcpu->arch.mmio_sign_extend = 1;
-	r = kvmppc_handle_load(run, vcpu, rt, bytes, is_default_endian);
-
-	return r;
+	return __kvmppc_handle_load(run, vcpu, rt, bytes, is_default_endian, 1);
 }
 
 int kvmppc_handle_store(struct kvm_run *run, struct kvm_vcpu *vcpu,