KVM: PPC: Emulator: clean up SPR reads and writes

When reading and writing SPRs, every SPR emulation piece had to read
or write the respective GPR the value was read from or stored in itself.

This approach is pretty prone to failure. What if we accidentally
implement mfspr emulation where we just do "break" and nothing else?
Suddenly we would get a random value in the return register - which is
always a bad idea.

So let's consolidate the generic code paths and only give the core
specific SPR handling code readily made variables to read/write from/to.

Functionally, this patch doesn't change anything, but it increases the
readability of the code and makes is less prone to bugs.

Signed-off-by: Alexander Graf <agraf@suse.de>

1 files changed, 12 insertions, 12 deletions

diff --git a/arch/powerpc/kvm/44x_emulate.c b/arch/powerpc/kvm/44x_emulate.c
index da81a2d92380..c8c61578fdfc 100644
--- a/arch/powerpc/kvm/44x_emulate.c
+++ b/arch/powerpc/kvm/44x_emulate.c
@@ -128,41 +128,41 @@ int kvmppc_core_emulate_op(struct kvm_run *run, struct kvm_vcpu *vcpu,
 	return emulated;
 }
 
-int kvmppc_core_emulate_mtspr(struct kvm_vcpu *vcpu, int sprn, int rs)
+int kvmppc_core_emulate_mtspr(struct kvm_vcpu *vcpu, int sprn, ulong spr_val)
 {
 	int emulated = EMULATE_DONE;
 
 	switch (sprn) {
 	case SPRN_PID:
-		kvmppc_set_pid(vcpu, kvmppc_get_gpr(vcpu, rs)); break;
+		kvmppc_set_pid(vcpu, spr_val); break;
 	case SPRN_MMUCR:
-		vcpu->arch.mmucr = kvmppc_get_gpr(vcpu, rs); break;
+		vcpu->arch.mmucr = spr_val; break;
 	case SPRN_CCR0:
-		vcpu->arch.ccr0 = kvmppc_get_gpr(vcpu, rs); break;
+		vcpu->arch.ccr0 = spr_val; break;
 	case SPRN_CCR1:
-		vcpu->arch.ccr1 = kvmppc_get_gpr(vcpu, rs); break;
+		vcpu->arch.ccr1 = spr_val; break;
 	default:
-		emulated = kvmppc_booke_emulate_mtspr(vcpu, sprn, rs);
+		emulated = kvmppc_booke_emulate_mtspr(vcpu, sprn, spr_val);
 	}
 
 	return emulated;
 }
 
-int kvmppc_core_emulate_mfspr(struct kvm_vcpu *vcpu, int sprn, int rt)
+int kvmppc_core_emulate_mfspr(struct kvm_vcpu *vcpu, int sprn, ulong *spr_val)
 {
 	int emulated = EMULATE_DONE;
 
 	switch (sprn) {
 	case SPRN_PID:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.pid); break;
+		*spr_val = vcpu->arch.pid; break;
 	case SPRN_MMUCR:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.mmucr); break;
+		*spr_val = vcpu->arch.mmucr; break;
 	case SPRN_CCR0:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.ccr0); break;
+		*spr_val = vcpu->arch.ccr0; break;
 	case SPRN_CCR1:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.ccr1); break;
+		*spr_val = vcpu->arch.ccr1; break;
 	default:
-		emulated = kvmppc_booke_emulate_mfspr(vcpu, sprn, rt);
+		emulated = kvmppc_booke_emulate_mfspr(vcpu, sprn, spr_val);
 	}
 
 	return emulated;