KVM: x86: Share emulator's common register decoding code

Remove all duplicate handling of register operands, including picking
the right register class and fetching it, by extracting a new function
that can be used for both REG and MODRM operands.

Centralize setting op->orig_val = op->val in fetch_register_operand()
as well.

No functional change intended.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Chang S. Bae <chang.seok.bae@intel.com>
Link: https://patch.msgid.link/20251114003633.60689-6-pbonzini@redhat.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 23019928734a6285d99ec754d151bc5d7e87293f..8a755ef30c182033673c875074057b2b5c036d95 100644 (file)
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -1026,6 +1026,7 @@ static void fetch_register_operand(struct operand *op)
                op->val = *(u64 *)op->addr.reg;
                break;
        }
+       op->orig_val = op->val;
 }
 
 static int em_fninit(struct x86_emulate_ctxt *ctxt)
@@ -1071,16 +1072,9 @@ static int em_fnstsw(struct x86_emulate_ctxt *ctxt)
        return X86EMUL_CONTINUE;
 }
 
-static void decode_register_operand(struct x86_emulate_ctxt *ctxt,
-                                   struct operand *op)
+static void __decode_register_operand(struct x86_emulate_ctxt *ctxt,
+                                     struct operand *op, int reg)
 {
-       unsigned int reg;
-
-       if (ctxt->d & ModRM)
-               reg = ctxt->modrm_reg;
-       else
-               reg = (ctxt->b & 7) | ((ctxt->rex_prefix & 1) << 3);
-
        if (ctxt->d & Sse) {
                op->type = OP_XMM;
                op->bytes = 16;
@@ -1099,9 +1093,20 @@ static void decode_register_operand(struct x86_emulate_ctxt *ctxt,
        op->type = OP_REG;
        op->bytes = (ctxt->d & ByteOp) ? 1 : ctxt->op_bytes;
        op->addr.reg = decode_register(ctxt, reg, ctxt->d & ByteOp);
-
        fetch_register_operand(op);
-       op->orig_val = op->val;
+}
+
+static void decode_register_operand(struct x86_emulate_ctxt *ctxt,
+                                   struct operand *op)
+{
+       unsigned int reg;
+
+       if (ctxt->d & ModRM)
+               reg = ctxt->modrm_reg;
+       else
+               reg = (ctxt->b & 7) | ((ctxt->rex_prefix & 1) << 3);
+
+       __decode_register_operand(ctxt, op, reg);
 }
 
 static void adjust_modrm_seg(struct x86_emulate_ctxt *ctxt, int base_reg)
@@ -1128,24 +1133,7 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt,
        ctxt->modrm_seg = VCPU_SREG_DS;
 
        if (ctxt->modrm_mod == 3 || (ctxt->d & NoMod)) {
-               op->type = OP_REG;
-               op->bytes = (ctxt->d & ByteOp) ? 1 : ctxt->op_bytes;
-               op->addr.reg = decode_register(ctxt, ctxt->modrm_rm,
-                               ctxt->d & ByteOp);
-               if (ctxt->d & Sse) {
-                       op->type = OP_XMM;
-                       op->bytes = 16;
-                       op->addr.xmm = ctxt->modrm_rm;
-                       kvm_read_sse_reg(ctxt->modrm_rm, &op->vec_val);
-                       return rc;
-               }
-               if (ctxt->d & Mmx) {
-                       op->type = OP_MM;
-                       op->bytes = 8;
-                       op->addr.mm = ctxt->modrm_rm & 7;
-                       return rc;
-               }
-               fetch_register_operand(op);
+               __decode_register_operand(ctxt, op, ctxt->modrm_rm);
                return rc;
        }
 
@@ -4619,14 +4607,12 @@ static int decode_operand(struct x86_emulate_ctxt *ctxt, struct operand *op,
                op->bytes = (ctxt->d & ByteOp) ? 1 : ctxt->op_bytes;
                op->addr.reg = reg_rmw(ctxt, VCPU_REGS_RAX);
                fetch_register_operand(op);
-               op->orig_val = op->val;
                break;
        case OpAccLo:
                op->type = OP_REG;
                op->bytes = (ctxt->d & ByteOp) ? 2 : ctxt->op_bytes;
                op->addr.reg = reg_rmw(ctxt, VCPU_REGS_RAX);
                fetch_register_operand(op);
-               op->orig_val = op->val;
                break;
        case OpAccHi:
                if (ctxt->d & ByteOp) {
@@ -4637,7 +4623,6 @@ static int decode_operand(struct x86_emulate_ctxt *ctxt, struct operand *op,
                op->bytes = ctxt->op_bytes;
                op->addr.reg = reg_rmw(ctxt, VCPU_REGS_RDX);
                fetch_register_operand(op);
-               op->orig_val = op->val;
                break;
        case OpDI:
                op->type = OP_MEM;