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, 52 insertions, 36 deletions

diff --git a/arch/powerpc/kvm/booke_emulate.c b/arch/powerpc/kvm/booke_emulate.c
index e14f7b2..6c76397 100644
--- a/arch/powerpc/kvm/booke_emulate.c
+++ b/arch/powerpc/kvm/booke_emulate.c
@@ -102,22 +102,26 @@ int kvmppc_booke_emulate_op(struct kvm_run *run, struct kvm_vcpu *vcpu,
  * will return the wrong result if called for them in another context
  * (such as debugging).
  */
-int kvmppc_booke_emulate_mtspr(struct kvm_vcpu *vcpu, int sprn, int rs)
+int kvmppc_booke_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_DEAR:
-		vcpu->arch.shared->dar = spr_val; break;
+		vcpu->arch.shared->dar = spr_val;
+		break;
 	case SPRN_ESR:
-		vcpu->arch.shared->esr = spr_val; break;
+		vcpu->arch.shared->esr = spr_val;
+		break;
 	case SPRN_DBCR0:
-		vcpu->arch.dbcr0 = spr_val; break;
+		vcpu->arch.dbcr0 = spr_val;
+		break;
 	case SPRN_DBCR1:
-		vcpu->arch.dbcr1 = spr_val; break;
+		vcpu->arch.dbcr1 = spr_val;
+		break;
 	case SPRN_DBSR:
-		vcpu->arch.dbsr &= ~spr_val; break;
+		vcpu->arch.dbsr &= ~spr_val;
+		break;
 	case SPRN_TSR:
 		kvmppc_clr_tsr_bits(vcpu, spr_val);
 		break;
@@ -131,13 +135,17 @@ int kvmppc_booke_emulate_mtspr(struct kvm_vcpu *vcpu, int sprn, int rs)
 	 * guest (PR-mode only).
 	 */
 	case SPRN_SPRG4:
-		vcpu->arch.shared->sprg4 = spr_val; break;
+		vcpu->arch.shared->sprg4 = spr_val;
+		break;
 	case SPRN_SPRG5:
-		vcpu->arch.shared->sprg5 = spr_val; break;
+		vcpu->arch.shared->sprg5 = spr_val;
+		break;
 	case SPRN_SPRG6:
-		vcpu->arch.shared->sprg6 = spr_val; break;
+		vcpu->arch.shared->sprg6 = spr_val;
+		break;
 	case SPRN_SPRG7:
-		vcpu->arch.shared->sprg7 = spr_val; break;
+		vcpu->arch.shared->sprg7 = spr_val;
+		break;
 
 	case SPRN_IVPR:
 		vcpu->arch.ivpr = spr_val;
@@ -207,75 +215,83 @@ int kvmppc_booke_emulate_mtspr(struct kvm_vcpu *vcpu, int sprn, int rs)
 	return emulated;
 }
 
-int kvmppc_booke_emulate_mfspr(struct kvm_vcpu *vcpu, int sprn, int rt)
+int kvmppc_booke_emulate_mfspr(struct kvm_vcpu *vcpu, int sprn, ulong *spr_val)
 {
 	int emulated = EMULATE_DONE;
 
 	switch (sprn) {
 	case SPRN_IVPR:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.ivpr); break;
+		*spr_val = vcpu->arch.ivpr;
+		break;
 	case SPRN_DEAR:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.shared->dar); break;
+		*spr_val = vcpu->arch.shared->dar;
+		break;
 	case SPRN_ESR:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.shared->esr); break;
+		*spr_val = vcpu->arch.shared->esr;
+		break;
 	case SPRN_DBCR0:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.dbcr0); break;
+		*spr_val = vcpu->arch.dbcr0;
+		break;
 	case SPRN_DBCR1:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.dbcr1); break;
+		*spr_val = vcpu->arch.dbcr1;
+		break;
 	case SPRN_DBSR:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.dbsr); break;
+		*spr_val = vcpu->arch.dbsr;
+		break;
 	case SPRN_TSR:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.tsr); break;
+		*spr_val = vcpu->arch.tsr;
+		break;
 	case SPRN_TCR:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.tcr); break;
+		*spr_val = vcpu->arch.tcr;
+		break;
 
 	case SPRN_IVOR0:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.ivor[BOOKE_IRQPRIO_CRITICAL]);
+		*spr_val = vcpu->arch.ivor[BOOKE_IRQPRIO_CRITICAL];
 		break;
 	case SPRN_IVOR1:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.ivor[BOOKE_IRQPRIO_MACHINE_CHECK]);
+		*spr_val = vcpu->arch.ivor[BOOKE_IRQPRIO_MACHINE_CHECK];
 		break;
 	case SPRN_IVOR2:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.ivor[BOOKE_IRQPRIO_DATA_STORAGE]);
+		*spr_val = vcpu->arch.ivor[BOOKE_IRQPRIO_DATA_STORAGE];
 		break;
 	case SPRN_IVOR3:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.ivor[BOOKE_IRQPRIO_INST_STORAGE]);
+		*spr_val = vcpu->arch.ivor[BOOKE_IRQPRIO_INST_STORAGE];
 		break;
 	case SPRN_IVOR4:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.ivor[BOOKE_IRQPRIO_EXTERNAL]);
+		*spr_val = vcpu->arch.ivor[BOOKE_IRQPRIO_EXTERNAL];
 		break;
 	case SPRN_IVOR5:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.ivor[BOOKE_IRQPRIO_ALIGNMENT]);
+		*spr_val = vcpu->arch.ivor[BOOKE_IRQPRIO_ALIGNMENT];
 		break;
 	case SPRN_IVOR6:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.ivor[BOOKE_IRQPRIO_PROGRAM]);
+		*spr_val = vcpu->arch.ivor[BOOKE_IRQPRIO_PROGRAM];
 		break;
 	case SPRN_IVOR7:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.ivor[BOOKE_IRQPRIO_FP_UNAVAIL]);
+		*spr_val = vcpu->arch.ivor[BOOKE_IRQPRIO_FP_UNAVAIL];
 		break;
 	case SPRN_IVOR8:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.ivor[BOOKE_IRQPRIO_SYSCALL]);
+		*spr_val = vcpu->arch.ivor[BOOKE_IRQPRIO_SYSCALL];
 		break;
 	case SPRN_IVOR9:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.ivor[BOOKE_IRQPRIO_AP_UNAVAIL]);
+		*spr_val = vcpu->arch.ivor[BOOKE_IRQPRIO_AP_UNAVAIL];
 		break;
 	case SPRN_IVOR10:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.ivor[BOOKE_IRQPRIO_DECREMENTER]);
+		*spr_val = vcpu->arch.ivor[BOOKE_IRQPRIO_DECREMENTER];
 		break;
 	case SPRN_IVOR11:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.ivor[BOOKE_IRQPRIO_FIT]);
+		*spr_val = vcpu->arch.ivor[BOOKE_IRQPRIO_FIT];
 		break;
 	case SPRN_IVOR12:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.ivor[BOOKE_IRQPRIO_WATCHDOG]);
+		*spr_val = vcpu->arch.ivor[BOOKE_IRQPRIO_WATCHDOG];
 		break;
 	case SPRN_IVOR13:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.ivor[BOOKE_IRQPRIO_DTLB_MISS]);
+		*spr_val = vcpu->arch.ivor[BOOKE_IRQPRIO_DTLB_MISS];
 		break;
 	case SPRN_IVOR14:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.ivor[BOOKE_IRQPRIO_ITLB_MISS]);
+		*spr_val = vcpu->arch.ivor[BOOKE_IRQPRIO_ITLB_MISS];
 		break;
 	case SPRN_IVOR15:
-		kvmppc_set_gpr(vcpu, rt, vcpu->arch.ivor[BOOKE_IRQPRIO_DEBUG]);
+		*spr_val = vcpu->arch.ivor[BOOKE_IRQPRIO_DEBUG];
 		break;
 
 	default: