KVM: PPC: Emulator: clean up instruction parsing

Instructions on PPC are pretty similarly encoded. So instead of
every instruction emulation code decoding the instruction fields
itself, we can move that code to more generic places and rely on
the compiler to optimize the unused bits away.

This has 2 advantages. It makes the code smaller and it makes the
code less error prone, as the instruction fields are always
available, so accidental misusage is reduced.

Functionally, this patch doesn't change anything.

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

1 files changed, 7 insertions, 20 deletions

diff --git a/arch/powerpc/kvm/44x_emulate.c b/arch/powerpc/kvm/44x_emulate.c
index 549bb2c9a47a..da81a2d92380 100644
--- a/arch/powerpc/kvm/44x_emulate.c
+++ b/arch/powerpc/kvm/44x_emulate.c
@@ -37,22 +37,19 @@ int kvmppc_core_emulate_op(struct kvm_run *run, struct kvm_vcpu *vcpu,
                            unsigned int inst, int *advance)
 {
 	int emulated = EMULATE_DONE;
-	int dcrn;
-	int ra;
-	int rb;
-	int rc;
-	int rs;
-	int rt;
-	int ws;
+	int dcrn = get_dcrn(inst);
+	int ra = get_ra(inst);
+	int rb = get_rb(inst);
+	int rc = get_rc(inst);
+	int rs = get_rs(inst);
+	int rt = get_rt(inst);
+	int ws = get_ws(inst);
 
 	switch (get_op(inst)) {
 	case 31:
 		switch (get_xop(inst)) {
 
 		case XOP_MFDCR:
-			dcrn = get_dcrn(inst);
-			rt = get_rt(inst);
-
 			/* The guest may access CPR0 registers to determine the timebase
 			 * frequency, and it must know the real host frequency because it
 			 * can directly access the timebase registers.
@@ -88,9 +85,6 @@ int kvmppc_core_emulate_op(struct kvm_run *run, struct kvm_vcpu *vcpu,
 			break;
 
 		case XOP_MTDCR:
-			dcrn = get_dcrn(inst);
-			rs = get_rs(inst);
-
 			/* emulate some access in kernel */
 			switch (dcrn) {
 			case DCRN_CPR0_CONFIG_ADDR:
@@ -108,17 +102,10 @@ int kvmppc_core_emulate_op(struct kvm_run *run, struct kvm_vcpu *vcpu,
 			break;
 
 		case XOP_TLBWE:
-			ra = get_ra(inst);
-			rs = get_rs(inst);
-			ws = get_ws(inst);
 			emulated = kvmppc_44x_emul_tlbwe(vcpu, ra, rs, ws);
 			break;
 
 		case XOP_TLBSX:
-			rt = get_rt(inst);
-			ra = get_ra(inst);
-			rb = get_rb(inst);
-			rc = get_rc(inst);
 			emulated = kvmppc_44x_emul_tlbsx(vcpu, rt, ra, rb, rc);
 			break;