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Commit 41061cdb authored by Bandan Das's avatar Bandan Das Committed by Paolo Bonzini
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KVM: emulate: do not initialize memopp 



rip_relative is only set if decode_modrm runs, and if you have ModRM
you will also have a memopp.  We can then access memopp unconditionally.
Note that rip_relative cannot be hoisted up to decode_modrm, or you
break "mov $0, xyz(%rip)".

Also, move typecast on "out of range value" of mem.ea to decode_modrm.

Together, all these optimizations save about 50 cycles on each emulated
instructions (4-6%).

Signed-off-by: default avatarBandan Das <bsd@redhat.com>
[Fix immediate operands with rip-relative addressing. - Paolo]
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 573e80fe

arch/x86/include/asm/kvm_emulate.h

+5 −0
Original line number Diff line number Diff line
@@ -295,6 +295,11 @@ struct x86_emulate_ctxt { 
	struct operand dst;

	int (*execute)(struct x86_emulate_ctxt *ctxt);

	int (*check_perm)(struct x86_emulate_ctxt *ctxt);

	/*

	 * The following six fields are cleared together,

	 * the rest are initialized unconditionally in x86_decode_insn

	 * or elsewhere

	 */

	bool rip_relative;

	u8 rex_prefix;

	u8 lock_prefix;

arch/x86/kvm/emulate.c

+4 −4
Original line number Diff line number Diff line
@@ -1177,6 +1177,9 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt, 
		}

	}

	op->addr.mem.ea = modrm_ea;

	if (ctxt->ad_bytes != 8)

		ctxt->memop.addr.mem.ea = (u32)ctxt->memop.addr.mem.ea;



done:

	return rc;

}
@@ -4425,9 +4428,6 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len) 


	ctxt->memop.addr.mem.seg = ctxt->seg_override;



	if (ctxt->memop.type == OP_MEM && ctxt->ad_bytes != 8)

		ctxt->memop.addr.mem.ea = (u32)ctxt->memop.addr.mem.ea;



	/*

	 * Decode and fetch the source operand: register, memory

	 * or immediate.
@@ -4448,7 +4448,7 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len) 
	rc = decode_operand(ctxt, &ctxt->dst, (ctxt->d >> DstShift) & OpMask);



done:

	if (ctxt->memopp && ctxt->memopp->type == OP_MEM && ctxt->rip_relative)

	if (ctxt->rip_relative)

		ctxt->memopp->addr.mem.ea += ctxt->_eip;



	return (rc != X86EMUL_CONTINUE) ? EMULATION_FAILED : EMULATION_OK;