KVM: x86 emulator: Specialize decoding for insns with 66/f2/f3 prefixes (0d7cdee8) · Commits · 戴 / test

arch/x86/kvm/emulate.c

+25 −1

Original line number	Diff line number	Diff line
		@@ -75,6 +75,7 @@
		#define Stack (1<<13) /* Stack instruction (push/pop) */
		#define Group (1<<14) /* Bits 3:5 of modrm byte extend opcode */
		#define GroupDual (1<<15) /* Alternate decoding of mod == 3 */
		#define Prefix (1<<16) /* Instruction varies with 66/f2/f3 prefix */
		/* Misc flags */
		#define VendorSpecific (1<<22) /* Vendor specific instruction */
		#define NoAccess (1<<23) /* Don't access memory (lea/invlpg/verr etc) */
		@@ -106,6 +107,7 @@ struct opcode {
		int (execute)(struct x86_emulate_ctxt ctxt);
		struct opcode *group;
		struct group_dual *gdual;
		struct gprefix *gprefix;
		} u;
		};

		@@ -114,6 +116,13 @@ struct group_dual {
		struct opcode mod3[8];
		};

		struct gprefix {
		struct opcode pfx_no;
		struct opcode pfx_66;
		struct opcode pfx_f2;
		struct opcode pfx_f3;
		};

		/* EFLAGS bit definitions. */
		#define EFLG_ID (1<<21)
		#define EFLG_VIP (1<<20)
		@@ -2625,7 +2634,8 @@ x86_decode_insn(struct x86_emulate_ctxt ctxt, void insn, int insn_len)
		struct decode_cache *c = &ctxt->decode;
		int rc = X86EMUL_CONTINUE;
		int mode = ctxt->mode;
		int def_op_bytes, def_ad_bytes, dual, goffset;
		int def_op_bytes, def_ad_bytes, dual, goffset, simd_prefix;
		bool op_prefix = false;
		struct opcode opcode, g_mod012, g_mod3;
		struct operand memop = { .type = OP_NONE };

		@@ -2662,6 +2672,7 @@ x86_decode_insn(struct x86_emulate_ctxt ctxt, void insn, int insn_len)
		for (;;) {
		switch (c->b = insn_fetch(u8, 1, c->eip)) {
		case 0x66: /* operand-size override */
		op_prefix = true;
		/* switch between 2/4 bytes */
		c->op_bytes = def_op_bytes ^ 6;
		break;
		@@ -2742,6 +2753,19 @@ done_prefixes:
		c->d \|= opcode.flags;
		}

		if (c->d & Prefix) {
		if (c->rep_prefix && op_prefix)
		return X86EMUL_UNHANDLEABLE;
		simd_prefix = op_prefix ? 0x66 : c->rep_prefix;
		switch (simd_prefix) {
		case 0x00: opcode = opcode.u.gprefix->pfx_no; break;
		case 0x66: opcode = opcode.u.gprefix->pfx_66; break;
		case 0xf2: opcode = opcode.u.gprefix->pfx_f2; break;
		case 0xf3: opcode = opcode.u.gprefix->pfx_f3; break;
		}
		c->d \|= opcode.flags;
		}

		c->execute = opcode.u.execute;

		/* Unrecognised? */

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