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Commit 9f4260e7 authored by Takuya Yoshikawa's avatar Takuya Yoshikawa Committed by Avi Kivity
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KVM: x86 emulator: Avoid pushing back ModRM byte fetched for group decoding 



Although ModRM byte is fetched for group decoding, it is soon pushed
back to make decode_modrm() fetch it later again.

Now that ModRM flag can be found in the top level opcode tables, fetch
ModRM byte before group decoding to make the code simpler.

Signed-off-by: default avatarTakuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: default avatarAvi Kivity <avi@redhat.com>
parent 1c2545be

arch/x86/kvm/emulate.c

+3 −5
Original line number Diff line number Diff line
@@ -972,7 +972,6 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt, 
		ctxt->modrm_rm = base_reg = (ctxt->rex_prefix & 1) << 3; /* REG.B */

	}



	ctxt->modrm = insn_fetch(u8, ctxt);

	ctxt->modrm_mod |= (ctxt->modrm & 0xc0) >> 6;

	ctxt->modrm_reg |= (ctxt->modrm & 0x38) >> 3;

	ctxt->modrm_rm |= (ctxt->modrm & 0x07);
@@ -3976,17 +3975,16 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len) 
	}

	ctxt->d = opcode.flags;



	if (ctxt->d & ModRM)

		ctxt->modrm = insn_fetch(u8, ctxt);



	while (ctxt->d & GroupMask) {

		switch (ctxt->d & GroupMask) {

		case Group:

			ctxt->modrm = insn_fetch(u8, ctxt);

			--ctxt->_eip;

			goffset = (ctxt->modrm >> 3) & 7;

			opcode = opcode.u.group[goffset];

			break;

		case GroupDual:

			ctxt->modrm = insn_fetch(u8, ctxt);

			--ctxt->_eip;

			goffset = (ctxt->modrm >> 3) & 7;

			if ((ctxt->modrm >> 6) == 3)

				opcode = opcode.u.gdual->mod3[goffset];