KVM: x86 emulator: simplify r/m decoding

Consolidate the duplicated code when not in any special case.

Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 4 insertions, 13 deletions

diff --git a/arch/x86/kvm/x86_emulate.c b/arch/x86/kvm/x86_emulate.c
index ca7ab2469a4..c3a823174f3 100644
--- a/arch/x86/kvm/x86_emulate.c
+++ b/arch/x86/kvm/x86_emulate.c
@@ -740,9 +740,7 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt,
                 c->modrm_ea = (u16)c->modrm_ea;
         } else {
                 /* 32/64-bit ModR/M decode. */
-                switch (c->modrm_rm) {
-                case 4:
-                case 12:
+                if ((c->modrm_rm & 7) == 4) {
                         sib = insn_fetch(u8, 1, c->eip);
                         index_reg |= (sib >> 3) & 7;
                         base_reg |= sib & 7;
@@ -754,18 +752,11 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt,
                                 c->modrm_ea += c->regs[base_reg];
                         if (index_reg != 4)
                                 c->modrm_ea += c->regs[index_reg] << scale;
-                        break;
-                case 5:
-                case 13:
-                        if (c->modrm_mod != 0)
-                                c->modrm_ea += c->regs[c->modrm_rm];
-                        else if (ctxt->mode == X86EMUL_MODE_PROT64)
+                } else if ((c->modrm_rm & 7) == 5 && c->modrm_mod == 0) {
+                        if (ctxt->mode == X86EMUL_MODE_PROT64)
                                 rip_relative = 1;
-                        break;
-                default:
+                } else
                         c->modrm_ea += c->regs[c->modrm_rm];
-                        break;
-                }
                 switch (c->modrm_mod) {
                 case 0:
                         if (c->modrm_rm == 5)