Refactor opcode lookup to clearly separate handling of different byte sequences and prefix types, in preparation for REX2 support. The decoder begins with a one-byte opcode table by default and falls through to other tables on escape bytes, but the logic is intertwined and hard to extend. REX2 introduces a dedicated bit in its payload byte to indicate which opcode table to use. To accommodate this mapping bit, the existing lookup path needs to be restructured. No functional changes intended. Signed-off-by: Chang S. Bae --- arch/x86/kvm/emulate.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-) diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c index 763fbd139242..9c98843094a1 100644 --- a/arch/x86/kvm/emulate.c +++ b/arch/x86/kvm/emulate.c @@ -4773,7 +4773,6 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len, int ctxt->_eip = ctxt->eip; ctxt->fetch.ptr = ctxt->fetch.data; ctxt->fetch.end = ctxt->fetch.data + insn_len; - ctxt->opcode_len = 1; ctxt->intercept = x86_intercept_none; if (insn_len > 0) memcpy(ctxt->fetch.data, insn, insn_len); @@ -4877,20 +4876,24 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len, int if (ctxt->rex.bits.w) ctxt->op_bytes = 8; - /* Opcode byte(s). */ - opcode = opcode_table[ctxt->b]; - /* Two-byte opcode? */ + /* Determine opcode byte(s): */ if (ctxt->b == 0x0f) { - ctxt->opcode_len = 2; + /* Escape byte: start two-byte opcode sequence */ ctxt->b = insn_fetch(u8, ctxt); - opcode = twobyte_table[ctxt->b]; - - /* 0F_38 opcode map */ if (ctxt->b == 0x38) { + /* Three-byte opcode */ ctxt->opcode_len = 3; ctxt->b = insn_fetch(u8, ctxt); opcode = opcode_map_0f_38[ctxt->b]; + } else { + /* Two-byte opcode */ + ctxt->opcode_len = 2; + opcode = twobyte_table[ctxt->b]; } + } else { + /* Single-byte opcode */ + ctxt->opcode_len = 1; + opcode = opcode_table[ctxt->b]; } ctxt->d = opcode.flags; -- 2.51.0