KVM: PPC: Teach MMIO Signedness

The guest I was trying to get to run uses the LHA and LHAU instructions.
Those instructions basically do a load, but also sign extend the result.

Since we need to fill our registers by hand when doing MMIO, we also need
to sign extend manually.

This patch implements sign extended MMIO and the LHA(U) instructions.

Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 29 insertions, 0 deletions

diff --git a/arch/powerpc/kvm/powerpc.c b/arch/powerpc/kvm/powerpc.c
index b7858b1e15e..1266ed02b47 100644
--- a/arch/powerpc/kvm/powerpc.c
+++ b/arch/powerpc/kvm/powerpc.c
@@ -301,6 +301,22 @@ static void kvmppc_complete_mmio_load(struct kvm_vcpu *vcpu,
                 }
         }
 
+        if (vcpu->arch.mmio_sign_extend) {
+                switch (run->mmio.len) {
+#ifdef CONFIG_PPC64
+                case 4:
+                        gpr = (s64)(s32)gpr;
+                        break;
+#endif
+                case 2:
+                        gpr = (s64)(s16)gpr;
+                        break;
+                case 1:
+                        gpr = (s64)(s8)gpr;
+                        break;
+                }
+        }
+
         kvmppc_set_gpr(vcpu, vcpu->arch.io_gpr, gpr);
 
         switch (vcpu->arch.io_gpr & KVM_REG_EXT_MASK) {
@@ -338,10 +354,23 @@ int kvmppc_handle_load(struct kvm_run *run, struct kvm_vcpu *vcpu,
         vcpu->arch.mmio_is_bigendian = is_bigendian;
         vcpu->mmio_needed = 1;
         vcpu->mmio_is_write = 0;
+        vcpu->arch.mmio_sign_extend = 0;
 
         return EMULATE_DO_MMIO;
 }
 
+/* Same as above, but sign extends */
+int kvmppc_handle_loads(struct kvm_run *run, struct kvm_vcpu *vcpu,
+                        unsigned int rt, unsigned int bytes, int is_bigendian)
+{
+        int r;
+
+        r = kvmppc_handle_load(run, vcpu, rt, bytes, is_bigendian);
+        vcpu->arch.mmio_sign_extend = 1;
+
+        return r;
+}
+
 int kvmppc_handle_store(struct kvm_run *run, struct kvm_vcpu *vcpu,
                         u64 val, unsigned int bytes, int is_bigendian)
 {