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, 16 insertions, 18 deletions

diff --git a/arch/powerpc/kvm/book3s_emulate.c b/arch/powerpc/kvm/book3s_emulate.c
index c023bcd253f..b9a989dc76c 100644
--- a/arch/powerpc/kvm/book3s_emulate.c
+++ b/arch/powerpc/kvm/book3s_emulate.c
@@ -318,10 +318,9 @@ static struct kvmppc_bat *kvmppc_find_bat(struct kvm_vcpu *vcpu, int sprn)
 	return bat;
 }
 
-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;
-	ulong spr_val = kvmppc_get_gpr(vcpu, rs);
 
 	switch (sprn) {
 	case SPRN_SDR1:
@@ -433,7 +432,7 @@ unprivileged:
 	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;
 
@@ -446,46 +445,46 @@ int kvmppc_core_emulate_mfspr(struct kvm_vcpu *vcpu, int sprn, int rt)
 		struct kvmppc_bat *bat = kvmppc_find_bat(vcpu, sprn);
 
 		if (sprn % 2)
-			kvmppc_set_gpr(vcpu, rt, bat->raw >> 32);
+			*spr_val = bat->raw >> 32;
 		else
-			kvmppc_set_gpr(vcpu, rt, bat->raw);
+			*spr_val = bat->raw;
 
 		break;
 	}
 	case SPRN_SDR1:
 		if (!spr_allowed(vcpu, PRIV_HYPER))
 			goto unprivileged;
-		kvmppc_set_gpr(vcpu, rt, to_book3s(vcpu)->sdr1);
+		*spr_val = to_book3s(vcpu)->sdr1;
 		break;
 	case SPRN_DSISR:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.shared->dsisr);
+		*spr_val = vcpu->arch.shared->dsisr;
 		break;
 	case SPRN_DAR:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.shared->dar);
+		*spr_val = vcpu->arch.shared->dar;
 		break;
 	case SPRN_HIOR:
-		kvmppc_set_gpr(vcpu, rt, to_book3s(vcpu)->hior);
+		*spr_val = to_book3s(vcpu)->hior;
 		break;
 	case SPRN_HID0:
-		kvmppc_set_gpr(vcpu, rt, to_book3s(vcpu)->hid[0]);
+		*spr_val = to_book3s(vcpu)->hid[0];
 		break;
 	case SPRN_HID1:
-		kvmppc_set_gpr(vcpu, rt, to_book3s(vcpu)->hid[1]);
+		*spr_val = to_book3s(vcpu)->hid[1];
 		break;
 	case SPRN_HID2:
 	case SPRN_HID2_GEKKO:
-		kvmppc_set_gpr(vcpu, rt, to_book3s(vcpu)->hid[2]);
+		*spr_val = to_book3s(vcpu)->hid[2];
 		break;
 	case SPRN_HID4:
 	case SPRN_HID4_GEKKO:
-		kvmppc_set_gpr(vcpu, rt, to_book3s(vcpu)->hid[4]);
+		*spr_val = to_book3s(vcpu)->hid[4];
 		break;
 	case SPRN_HID5:
-		kvmppc_set_gpr(vcpu, rt, to_book3s(vcpu)->hid[5]);
+		*spr_val = to_book3s(vcpu)->hid[5];
 		break;
 	case SPRN_CFAR:
 	case SPRN_PURR:
-		kvmppc_set_gpr(vcpu, rt, 0);
+		*spr_val = 0;
 		break;
 	case SPRN_GQR0:
 	case SPRN_GQR1:
@@ -495,8 +494,7 @@ int kvmppc_core_emulate_mfspr(struct kvm_vcpu *vcpu, int sprn, int rt)
 	case SPRN_GQR5:
 	case SPRN_GQR6:
 	case SPRN_GQR7:
-		kvmppc_set_gpr(vcpu, rt,
-			       to_book3s(vcpu)->gqr[sprn - SPRN_GQR0]);
+		*spr_val = to_book3s(vcpu)->gqr[sprn - SPRN_GQR0];
 		break;
 	case SPRN_THRM1:
 	case SPRN_THRM2:
@@ -511,7 +509,7 @@ int kvmppc_core_emulate_mfspr(struct kvm_vcpu *vcpu, int sprn, int rt)
 	case SPRN_PMC3_GEKKO:
 	case SPRN_PMC4_GEKKO:
 	case SPRN_WPAR_GEKKO:
-		kvmppc_set_gpr(vcpu, rt, 0);
+		*spr_val = 0;
 		break;
 	default:
 unprivileged: