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Subject: [PATCH 12/14] KVM: x86 emulator
From: Avi Kivity <avi@qumranet.com>
Date: Sun, 05 Nov 2006 20:40:35 -0000
To: kvm-devel@lists.sourceforge.net
Cc: linux-kernel@vger.kernel.org, akpm@osdl.org
References: <454E4941.7000108@qumranet.com>
In-Reply-To: <454E4941.7000108@qumranet.com>
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Add an x86 instruction emulator for kvm.

We need an x86 emulator for the following reasons:

- mmio instructions are intercepted as page faults, with no information about
  the operation to be performed other than the virtual address
- real-mode is emulated using the old-fashined vm86 mode, with no special
  intercepts for the privileged instructions, so we need to emulate mov cr,
  lgdt, and lidt
- we plan to cache shadow page tables in the future, so that a guest context
  switch will not throw away all the mappings we worked so hard to build.  but
  cachine page tables means write-protecting the guest page tables to keep
  them in sync, so any writes to the guest page tables need to be emulated

The emulator was lifted from the Xen hypervisor.

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

Index: linux-2.6/drivers/kvm/x86_emulate.c
===================================================================
--- /dev/null
+++ linux-2.6/drivers/kvm/x86_emulate.c
@@ -0,0 +1,1370 @@
+/******************************************************************************
+ * x86_emulate.c
+ *
+ * Generic x86 (32-bit and 64-bit) instruction decoder and emulator.
+ *
+ * Copyright (c) 2005 Keir Fraser
+ *
+ * Linux coding style, mod r/m decoder, segment base fixes, real-mode
+ * privieged instructions:
+ *
+ * Copyright (C) 2006 Qumranet
+ *
+ *   Avi Kivity <avi@qumranet.com>
+ *   Yaniv Kamay <yaniv@qumranet.com>
+ *
+ * From: xen-unstable 10676:af9809f51f81a3c43f276f00c81a52ef558afda4
+ */
+
+#ifndef __KERNEL__
+#include <stdio.h>
+#include <stdint.h>
+#include <public/xen.h>
+#define DPRINTF(_f, _a ...) printf( _f , ## _a )
+#else
+#include "kvm.h"
+#define DPRINTF(x...) do {} while (0)
+#endif
+#include "x86_emulate.h"
+
+/*
+ * Opcode effective-address decode tables.
+ * Note that we only emulate instructions that have at least one memory
+ * operand (excluding implicit stack references). We assume that stack
+ * references and instruction fetches will never occur in special memory
+ * areas that require emulation. So, for example, 'mov <imm>,<reg>' need
+ * not be handled.
+ */
+
+/* Operand sizes: 8-bit operands or specified/overridden size. */
+#define ByteOp      (1<<0)	/* 8-bit operands. */
+/* Destination operand type. */
+#define ImplicitOps (1<<1)	/* Implicit in opcode. No generic decode. */
+#define DstReg      (2<<1)	/* Register operand. */
+#define DstMem      (3<<1)	/* Memory operand. */
+#define DstMask     (3<<1)
+/* Source operand type. */
+#define SrcNone     (0<<3)	/* No source operand. */
+#define SrcImplicit (0<<3)	/* Source operand is implicit in the opcode. */
+#define SrcReg      (1<<3)	/* Register operand. */
+#define SrcMem      (2<<3)	/* Memory operand. */
+#define SrcMem16    (3<<3)	/* Memory operand (16-bit). */
+#define SrcMem32    (4<<3)	/* Memory operand (32-bit). */
+#define SrcImm      (5<<3)	/* Immediate operand. */
+#define SrcImmByte  (6<<3)	/* 8-bit sign-extended immediate operand. */
+#define SrcMask     (7<<3)
+/* Generic ModRM decode. */
+#define ModRM       (1<<6)
+/* Destination is only written; never read. */
+#define Mov         (1<<7)
+
+static u8 opcode_table[256] = {
+	/* 0x00 - 0x07 */
+	ByteOp | DstMem | SrcReg | ModRM, DstMem | SrcReg | ModRM,
+	ByteOp | DstReg | SrcMem | ModRM, DstReg | SrcMem | ModRM,
+	0, 0, 0, 0,
+	/* 0x08 - 0x0F */
+	ByteOp | DstMem | SrcReg | ModRM, DstMem | SrcReg | ModRM,
+	ByteOp | DstReg | SrcMem | ModRM, DstReg | SrcMem | ModRM,
+	0, 0, 0, 0,
+	/* 0x10 - 0x17 */
+	ByteOp | DstMem | SrcReg | ModRM, DstMem | SrcReg | ModRM,
+	ByteOp | DstReg | SrcMem | ModRM, DstReg | SrcMem | ModRM,
+	0, 0, 0, 0,
+	/* 0x18 - 0x1F */
+	ByteOp | DstMem | SrcReg | ModRM, DstMem | SrcReg | ModRM,
+	ByteOp | DstReg | SrcMem | ModRM, DstReg | SrcMem | ModRM,
+	0, 0, 0, 0,
+	/* 0x20 - 0x27 */
+	ByteOp | DstMem | SrcReg | ModRM, DstMem | SrcReg | ModRM,
+	ByteOp | DstReg | SrcMem | ModRM, DstReg | SrcMem | ModRM,
+	0, 0, 0, 0,
+	/* 0x28 - 0x2F */
+	ByteOp | DstMem | SrcReg | ModRM, DstMem | SrcReg | ModRM,
+	ByteOp | DstReg | SrcMem | ModRM, DstReg | SrcMem | ModRM,
+	0, 0, 0, 0,
+	/* 0x30 - 0x37 */
+	ByteOp | DstMem | SrcReg | ModRM, DstMem | SrcReg | ModRM,
+	ByteOp | DstReg | SrcMem | ModRM, DstReg | SrcMem | ModRM,
+	0, 0, 0, 0,
+	/* 0x38 - 0x3F */
+	ByteOp | DstMem | SrcReg | ModRM, DstMem | SrcReg | ModRM,
+	ByteOp | DstReg | SrcMem | ModRM, DstReg | SrcMem | ModRM,
+	0, 0, 0, 0,
+	/* 0x40 - 0x4F */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	/* 0x50 - 0x5F */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	/* 0x60 - 0x6F */
+	0, 0, 0, DstReg | SrcMem32 | ModRM | Mov /* movsxd (x86/64) */ ,
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	/* 0x70 - 0x7F */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	/* 0x80 - 0x87 */
+	ByteOp | DstMem | SrcImm | ModRM, DstMem | SrcImm | ModRM,
+	ByteOp | DstMem | SrcImm | ModRM, DstMem | SrcImmByte | ModRM,
+	ByteOp | DstMem | SrcReg | ModRM, DstMem | SrcReg | ModRM,
+	ByteOp | DstMem | SrcReg | ModRM, DstMem | SrcReg | ModRM,
+	/* 0x88 - 0x8F */
+	ByteOp | DstMem | SrcReg | ModRM | Mov, DstMem | SrcReg | ModRM | Mov,
+	ByteOp | DstReg | SrcMem | ModRM | Mov, DstReg | SrcMem | ModRM | Mov,
+	0, 0, 0, DstMem | SrcNone | ModRM | Mov,
+	/* 0x90 - 0x9F */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	/* 0xA0 - 0xA7 */
+	ByteOp | DstReg | SrcMem | Mov, DstReg | SrcMem | Mov,
+	ByteOp | DstMem | SrcReg | Mov, DstMem | SrcReg | Mov,
+	ByteOp | ImplicitOps | Mov, ImplicitOps | Mov,
+	ByteOp | ImplicitOps, ImplicitOps,
+	/* 0xA8 - 0xAF */
+	0, 0, ByteOp | ImplicitOps | Mov, ImplicitOps | Mov,
+	ByteOp | ImplicitOps | Mov, ImplicitOps | Mov,
+	ByteOp | ImplicitOps, ImplicitOps,
+	/* 0xB0 - 0xBF */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	/* 0xC0 - 0xC7 */
+	ByteOp | DstMem | SrcImm | ModRM, DstMem | SrcImmByte | ModRM, 0, 0,
+	0, 0, ByteOp | DstMem | SrcImm | ModRM | Mov,
+	    DstMem | SrcImm | ModRM | Mov,
+	/* 0xC8 - 0xCF */
+	0, 0, 0, 0, 0, 0, 0, 0,
+	/* 0xD0 - 0xD7 */
+	ByteOp | DstMem | SrcImplicit | ModRM, DstMem | SrcImplicit | ModRM,
+	ByteOp | DstMem | SrcImplicit | ModRM, DstMem | SrcImplicit | ModRM,
+	0, 0, 0, 0,
+	/* 0xD8 - 0xDF */
+	0, 0, 0, 0, 0, 0, 0, 0,
+	/* 0xE0 - 0xEF */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	/* 0xF0 - 0xF7 */
+	0, 0, 0, 0,
+	0, 0, ByteOp | DstMem | SrcNone | ModRM, DstMem | SrcNone | ModRM,
+	/* 0xF8 - 0xFF */
+	0, 0, 0, 0,
+	0, 0, ByteOp | DstMem | SrcNone | ModRM, DstMem | SrcNone | ModRM
+};
+
+static u8 twobyte_table[256] = {
+	/* 0x00 - 0x0F */
+	0, SrcMem | ModRM | DstReg | Mov, 0, 0, 0, 0, 0, 0,
+	0, 0, 0, 0, 0, ImplicitOps | ModRM, 0, 0,
+	/* 0x10 - 0x1F */
+	0, 0, 0, 0, 0, 0, 0, 0, ImplicitOps | ModRM, 0, 0, 0, 0, 0, 0, 0,
+	/* 0x20 - 0x2F */
+	ImplicitOps, 0, ImplicitOps, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	/* 0x30 - 0x3F */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	/* 0x40 - 0x47 */
+	DstReg | SrcMem | ModRM | Mov, DstReg | SrcMem | ModRM | Mov,
+	DstReg | SrcMem | ModRM | Mov, DstReg | SrcMem | ModRM | Mov,
+	DstReg | SrcMem | ModRM | Mov, DstReg | SrcMem | ModRM | Mov,
+	DstReg | SrcMem | ModRM | Mov, DstReg | SrcMem | ModRM | Mov,
+	/* 0x48 - 0x4F */
+	DstReg | SrcMem | ModRM | Mov, DstReg | SrcMem | ModRM | Mov,
+	DstReg | SrcMem | ModRM | Mov, DstReg | SrcMem | ModRM | Mov,
+	DstReg | SrcMem | ModRM | Mov, DstReg | SrcMem | ModRM | Mov,
+	DstReg | SrcMem | ModRM | Mov, DstReg | SrcMem | ModRM | Mov,
+	/* 0x50 - 0x5F */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	/* 0x60 - 0x6F */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	/* 0x70 - 0x7F */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	/* 0x80 - 0x8F */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	/* 0x90 - 0x9F */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	/* 0xA0 - 0xA7 */
+	0, 0, 0, DstMem | SrcReg | ModRM, 0, 0, 0, 0,
+	/* 0xA8 - 0xAF */
+	0, 0, 0, DstMem | SrcReg | ModRM, 0, 0, 0, 0,
+	/* 0xB0 - 0xB7 */
+	ByteOp | DstMem | SrcReg | ModRM, DstMem | SrcReg | ModRM, 0,
+	    DstMem | SrcReg | ModRM,
+	0, 0, ByteOp | DstReg | SrcMem | ModRM | Mov,
+	    DstReg | SrcMem16 | ModRM | Mov,
+	/* 0xB8 - 0xBF */
+	0, 0, DstMem | SrcImmByte | ModRM, DstMem | SrcReg | ModRM,
+	0, 0, ByteOp | DstReg | SrcMem | ModRM | Mov,
+	    DstReg | SrcMem16 | ModRM | Mov,
+	/* 0xC0 - 0xCF */
+	0, 0, 0, 0, 0, 0, 0, ImplicitOps | ModRM, 0, 0, 0, 0, 0, 0, 0, 0,
+	/* 0xD0 - 0xDF */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	/* 0xE0 - 0xEF */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+	/* 0xF0 - 0xFF */
+	0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
+};
+
+/* Type, address-of, and value of an instruction's operand. */
+struct operand {
+	enum { OP_REG, OP_MEM, OP_IMM } type;
+	unsigned int bytes;
+	unsigned long val, orig_val, *ptr;
+};
+
+/* EFLAGS bit definitions. */
+#define EFLG_OF (1<<11)
+#define EFLG_DF (1<<10)
+#define EFLG_SF (1<<7)
+#define EFLG_ZF (1<<6)
+#define EFLG_AF (1<<4)
+#define EFLG_PF (1<<2)
+#define EFLG_CF (1<<0)
+
+/*
+ * Instruction emulation:
+ * Most instructions are emulated directly via a fragment of inline assembly
+ * code. This allows us to save/restore EFLAGS and thus very easily pick up
+ * any modified flags.
+ */
+
+#if defined(__x86_64__)
+#define _LO32 "k"		/* force 32-bit operand */
+#define _STK  "%%rsp"		/* stack pointer */
+#elif defined(__i386__)
+#define _LO32 ""		/* force 32-bit operand */
+#define _STK  "%%esp"		/* stack pointer */
+#endif
+
+/*
+ * These EFLAGS bits are restored from saved value during emulation, and
+ * any changes are written back to the saved value after emulation.
+ */
+#define EFLAGS_MASK (EFLG_OF|EFLG_SF|EFLG_ZF|EFLG_AF|EFLG_PF|EFLG_CF)
+
+/* Before executing instruction: restore necessary bits in EFLAGS. */
+#define _PRE_EFLAGS(_sav, _msk, _tmp) \
+	/* EFLAGS = (_sav & _msk) | (EFLAGS & ~_msk); */	\
+	"push %"_sav"; "					\
+	"movl %"_msk",%"_LO32 _tmp"; "				\
+	"andl %"_LO32 _tmp",("_STK"); "				\
+	"pushf; "						\
+	"notl %"_LO32 _tmp"; "					\
+	"andl %"_LO32 _tmp",("_STK"); "				\
+	"pop  %"_tmp"; "					\
+	"orl  %"_LO32 _tmp",("_STK"); "				\
+	"popf; "						\
+	/* _sav &= ~msk; */					\
+	"movl %"_msk",%"_LO32 _tmp"; "				\
+	"notl %"_LO32 _tmp"; "					\
+	"andl %"_LO32 _tmp",%"_sav"; "
+
+/* After executing instruction: write-back necessary bits in EFLAGS. */
+#define _POST_EFLAGS(_sav, _msk, _tmp) \
+	/* _sav |= EFLAGS & _msk; */		\
+	"pushf; "				\
+	"pop  %"_tmp"; "			\
+	"andl %"_msk",%"_LO32 _tmp"; "		\
+	"orl  %"_LO32 _tmp",%"_sav"; "
+
+/* Raw emulation: instruction has two explicit operands. */
+#define __emulate_2op_nobyte(_op,_src,_dst,_eflags,_wx,_wy,_lx,_ly,_qx,_qy) \
+	do { 								    \
+		unsigned long _tmp;					    \
+									    \
+		switch ((_dst).bytes) {					    \
+		case 2:							    \
+			__asm__ __volatile__ (				    \
+				_PRE_EFLAGS("0","4","2")		    \
+				_op"w %"_wx"3,%1; "			    \
+				_POST_EFLAGS("0","4","2")		    \
+				: "=m" (_eflags), "=m" ((_dst).val),        \
+				  "=&r" (_tmp)				    \
+				: _wy ((_src).val), "i" (EFLAGS_MASK) );    \
+			break;						    \
+		case 4:							    \
+			__asm__ __volatile__ (				    \
+				_PRE_EFLAGS("0","4","2")		    \
+				_op"l %"_lx"3,%1; "			    \
+				_POST_EFLAGS("0","4","2")		    \
+				: "=m" (_eflags), "=m" ((_dst).val),	    \
+				  "=&r" (_tmp)				    \
+				: _ly ((_src).val), "i" (EFLAGS_MASK) );    \
+			break;						    \
+		case 8:							    \
+			__emulate_2op_8byte(_op, _src, _dst,		    \
+					    _eflags, _qx, _qy);		    \
+			break;						    \
+		}							    \
+	} while (0)
+
+#define __emulate_2op(_op,_src,_dst,_eflags,_bx,_by,_wx,_wy,_lx,_ly,_qx,_qy) \
+	do {								     \
+		unsigned long _tmp;					     \
+		switch ( (_dst).bytes )					     \
+		{							     \
+		case 1:							     \
+			__asm__ __volatile__ (				     \
+				_PRE_EFLAGS("0","4","2")		     \
+				_op"b %"_bx"3,%1; "			     \
+				_POST_EFLAGS("0","4","2")		     \
+				: "=m" (_eflags), "=m" ((_dst).val),	     \
+				  "=&r" (_tmp)				     \
+				: _by ((_src).val), "i" (EFLAGS_MASK) );     \
+			break;						     \
+		default:						     \
+			__emulate_2op_nobyte(_op, _src, _dst, _eflags,	     \
+					     _wx, _wy, _lx, _ly, _qx, _qy);  \
+			break;						     \
+		}							     \
+	} while (0)
+
+/* Source operand is byte-sized and may be restricted to just %cl. */
+#define emulate_2op_SrcB(_op, _src, _dst, _eflags)                      \
+	__emulate_2op(_op, _src, _dst, _eflags,				\
+		      "b", "c", "b", "c", "b", "c", "b", "c")
+
+/* Source operand is byte, word, long or quad sized. */
+#define emulate_2op_SrcV(_op, _src, _dst, _eflags)                      \
+	__emulate_2op(_op, _src, _dst, _eflags,				\
+		      "b", "q", "w", "r", _LO32, "r", "", "r")
+
+/* Source operand is word, long or quad sized. */
+#define emulate_2op_SrcV_nobyte(_op, _src, _dst, _eflags)               \
+	__emulate_2op_nobyte(_op, _src, _dst, _eflags,			\
+			     "w", "r", _LO32, "r", "", "r")
+
+/* Instruction has only one explicit operand (no source operand). */
+#define emulate_1op(_op, _dst, _eflags)                                    \
+	do {								\
+		unsigned long _tmp;					\
+									\
+		switch ( (_dst).bytes )					\
+		{							\
+		case 1:							\
+			__asm__ __volatile__ (				\
+				_PRE_EFLAGS("0","3","2")		\
+				_op"b %1; "				\
+				_POST_EFLAGS("0","3","2")		\
+				: "=m" (_eflags), "=m" ((_dst).val),	\
+				  "=&r" (_tmp)				\
+				: "i" (EFLAGS_MASK) );			\
+			break;						\
+		case 2:							\
+			__asm__ __volatile__ (				\
+				_PRE_EFLAGS("0","3","2")		\
+				_op"w %1; "				\
+				_POST_EFLAGS("0","3","2")		\
+				: "=m" (_eflags), "=m" ((_dst).val),	\
+				  "=&r" (_tmp)				\
+				: "i" (EFLAGS_MASK) );			\
+			break;						\
+		case 4:							\
+			__asm__ __volatile__ (				\
+				_PRE_EFLAGS("0","3","2")		\
+				_op"l %1; "				\
+				_POST_EFLAGS("0","3","2")		\
+				: "=m" (_eflags), "=m" ((_dst).val),	\
+				  "=&r" (_tmp)				\
+				: "i" (EFLAGS_MASK) );			\
+			break;						\
+		case 8:							\
+			__emulate_1op_8byte(_op, _dst, _eflags);	\
+			break;						\
+		}							\
+	} while (0)
+
+/* Emulate an instruction with quadword operands (x86/64 only). */
+#if defined(__x86_64__)
+#define __emulate_2op_8byte(_op, _src, _dst, _eflags, _qx, _qy)           \
+	do {								  \
+		__asm__ __volatile__ (					  \
+			_PRE_EFLAGS("0","4","2")			  \
+			_op"q %"_qx"3,%1; "				  \
+			_POST_EFLAGS("0","4","2")			  \
+			: "=m" (_eflags), "=m" ((_dst).val), "=&r" (_tmp) \
+			: _qy ((_src).val), "i" (EFLAGS_MASK) );	  \
+	} while (0)
+
+#define __emulate_1op_8byte(_op, _dst, _eflags)                           \
+	do {								  \
+		__asm__ __volatile__ (					  \
+			_PRE_EFLAGS("0","3","2")			  \
+			_op"q %1; "					  \
+			_POST_EFLAGS("0","3","2")			  \
+			: "=m" (_eflags), "=m" ((_dst).val), "=&r" (_tmp) \
+			: "i" (EFLAGS_MASK) );				  \
+	} while (0)
+
+#elif defined(__i386__)
+#define __emulate_2op_8byte(_op, _src, _dst, _eflags, _qx, _qy)
+#define __emulate_1op_8byte(_op, _dst, _eflags)
+#endif				/* __i386__ */
+
+/* Fetch next part of the instruction being emulated. */
+#define insn_fetch(_type, _size, _eip)                                  \
+({	unsigned long _x;						\
+	rc = ops->read_std((unsigned long)(_eip) + ctxt->cs_base, &_x,	\
+                                                  (_size), ctxt);       \
+	if ( rc != 0 )							\
+		goto done;						\
+	(_eip) += (_size);						\
+	(_type)_x;							\
+})
+
+/* Access/update address held in a register, based on addressing mode. */
+#define register_address(base, reg)                                     \
+	((base) + ((ad_bytes == sizeof(unsigned long)) ? (reg) :	\
+		   ((reg) & ((1UL << (ad_bytes << 3)) - 1))))
+
+#define register_address_increment(reg, inc)                            \
+	do {								\
+		/* signed type ensures sign extension to long */        \
+		int _inc = (inc);					\
+		if ( ad_bytes == sizeof(unsigned long) )		\
+			(reg) += _inc;					\
+		else							\
+			(reg) = ((reg) & ~((1UL << (ad_bytes << 3)) - 1)) | \
+			   (((reg) + _inc) & ((1UL << (ad_bytes << 3)) - 1)); \
+	} while (0)
+
+void *decode_register(u8 modrm_reg, unsigned long *regs,
+		      int highbyte_regs)
+{
+	void *p;
+
+	p = &regs[modrm_reg];
+	if (highbyte_regs && modrm_reg >= 4 && modrm_reg < 8)
+		p = (unsigned char *)&regs[modrm_reg & 3] + 1;
+	return p;
+}
+
+static int read_descriptor(struct x86_emulate_ctxt *ctxt,
+			   struct x86_emulate_ops *ops,
+			   void *ptr,
+			   u16 *size, unsigned long *address, int op_bytes)
+{
+	int rc;
+
+	if (op_bytes == 2)
+		op_bytes = 3;
+	*address = 0;
+	rc = ops->read_std((unsigned long)ptr, (unsigned long *)size, 2, ctxt);
+	if (rc)
+		return rc;
+	rc = ops->read_std((unsigned long)ptr + 2, address, op_bytes, ctxt);
+	return rc;
+}
+
+int
+x86_emulate_memop(struct x86_emulate_ctxt *ctxt, struct x86_emulate_ops *ops)
+{
+	u8 b, d, sib, twobyte = 0, rex_prefix = 0;
+	u8 modrm, modrm_mod = 0, modrm_reg = 0, modrm_rm = 0;
+	unsigned long *override_base = NULL;
+	unsigned int op_bytes, ad_bytes, lock_prefix = 0, rep_prefix = 0, i;
+	int rc = 0;
+	struct operand src, dst;
+	unsigned long cr2 = ctxt->cr2;
+	int mode = ctxt->mode;
+	unsigned long modrm_ea;
+	int use_modrm_ea, index_reg = 0, base_reg = 0, scale, rip_relative = 0;
+
+	/* Shadow copy of register state. Committed on successful emulation. */
+	unsigned long _regs[NR_VCPU_REGS];
+	unsigned long _eip = ctxt->vcpu->rip, _eflags = ctxt->eflags;
+	unsigned long modrm_val = 0;
+
+	memcpy(_regs, ctxt->vcpu->regs, sizeof _regs);
+
+	switch (mode) {
+	case X86EMUL_MODE_REAL:
+	case X86EMUL_MODE_PROT16:
+		op_bytes = ad_bytes = 2;
+		break;
+	case X86EMUL_MODE_PROT32:
+		op_bytes = ad_bytes = 4;
+		break;
+#ifdef __x86_64__
+	case X86EMUL_MODE_PROT64:
+		op_bytes = 4;
+		ad_bytes = 8;
+		break;
+#endif
+	default:
+		return -1;
+	}
+
+	/* Legacy prefixes. */
+	for (i = 0; i < 8; i++) {
+		switch (b = insn_fetch(u8, 1, _eip)) {
+		case 0x66:	/* operand-size override */
+			op_bytes ^= 6;	/* switch between 2/4 bytes */
+			break;
+		case 0x67:	/* address-size override */
+			if (mode == X86EMUL_MODE_PROT64)
+				ad_bytes ^= 12;	/* switch between 4/8 bytes */
+			else
+				ad_bytes ^= 6;	/* switch between 2/4 bytes */
+			break;
+		case 0x2e:	/* CS override */
+			override_base = &ctxt->cs_base;
+			break;
+		case 0x3e:	/* DS override */
+			override_base = &ctxt->ds_base;
+			break;
+		case 0x26:	/* ES override */
+			override_base = &ctxt->es_base;
+			break;
+		case 0x64:	/* FS override */
+			override_base = &ctxt->fs_base;
+			break;
+		case 0x65:	/* GS override */
+			override_base = &ctxt->gs_base;
+			break;
+		case 0x36:	/* SS override */
+			override_base = &ctxt->ss_base;
+			break;
+		case 0xf0:	/* LOCK */
+			lock_prefix = 1;
+			break;
+		case 0xf3:	/* REP/REPE/REPZ */
+			rep_prefix = 1;
+			break;
+		case 0xf2:	/* REPNE/REPNZ */
+			break;
+		default:
+			goto done_prefixes;
+		}
+	}
+
+done_prefixes:
+
+	/* REX prefix. */
+	if ((mode == X86EMUL_MODE_PROT64) && ((b & 0xf0) == 0x40)) {
+		rex_prefix = b;
+		if (b & 8)
+			op_bytes = 8;	/* REX.W */
+		modrm_reg = (b & 4) << 1;	/* REX.R */
+		index_reg = (b & 2) << 2; /* REX.X */
+		modrm_rm = base_reg = (b & 1) << 3; /* REG.B */
+		b = insn_fetch(u8, 1, _eip);
+	}
+
+	/* Opcode byte(s). */
+	d = opcode_table[b];
+	if (d == 0) {
+		/* Two-byte opcode? */
+		if (b == 0x0f) {
+			twobyte = 1;
+			b = insn_fetch(u8, 1, _eip);
+			d = twobyte_table[b];
+		}
+
+		/* Unrecognised? */
+		if (d == 0)
+			goto cannot_emulate;
+	}
+
+	/* ModRM and SIB bytes. */
+	if (d & ModRM) {
+		modrm = insn_fetch(u8, 1, _eip);
+		modrm_mod |= (modrm & 0xc0) >> 6;
+		modrm_reg |= (modrm & 0x38) >> 3;
+		modrm_rm |= (modrm & 0x07);
+		modrm_ea = 0;
+		use_modrm_ea = 1;
+
+		if (modrm_mod == 3) {
+			modrm_val = *(unsigned long *)
+				decode_register(modrm_rm, _regs, d & ByteOp);
+			goto modrm_done;
+		}
+
+		if (ad_bytes == 2) {
+			unsigned bx = _regs[VCPU_REGS_RBX];
+			unsigned bp = _regs[VCPU_REGS_RBP];
+			unsigned si = _regs[VCPU_REGS_RSI];
+			unsigned di = _regs[VCPU_REGS_RDI];
+
+			/* 16-bit ModR/M decode. */
+			switch (modrm_mod) {
+			case 0:
+				if (modrm_rm == 6)
+					modrm_ea += insn_fetch(u16, 2, _eip);
+				break;
+			case 1:
+				modrm_ea += insn_fetch(s8, 1, _eip);
+				break;
+			case 2:
+				modrm_ea += insn_fetch(u16, 2, _eip);
+				break;
+			}
+			switch (modrm_rm) {
+			case 0:
+				modrm_ea += bx + si;
+				break;
+			case 1:
+				modrm_ea += bx + di;
+				break;
+			case 2:
+				modrm_ea += bp + si;
+				break;
+			case 3:
+				modrm_ea += bp + di;
+				break;
+			case 4:
+				modrm_ea += si;
+				break;
+			case 5:
+				modrm_ea += di;
+				break;
+			case 6:
+				if (modrm_mod != 0)
+					modrm_ea += bp;
+				break;
+			case 7:
+				modrm_ea += bx;
+				break;
+			}
+			if (modrm_rm == 2 || modrm_rm == 3 ||
+			    (modrm_rm == 6 && modrm_mod != 0))
+				if (!override_base)
+					override_base = &ctxt->ss_base;
+			modrm_ea = (u16)modrm_ea;
+		} else {
+			/* 32/64-bit ModR/M decode. */
+			switch (modrm_rm) {
+			case 4:
+			case 12:
+				sib = insn_fetch(u8, 1, _eip);
+				index_reg |= (sib >> 3) & 7;
+				base_reg |= sib & 7;
+				scale = sib >> 6;
+
+				switch (base_reg) {
+				case 5:
+					if (modrm_mod != 0)
+						modrm_ea += _regs[base_reg];
+					else
+						modrm_ea += insn_fetch(s32, 4, _eip);
+					break;
+				default:
+					modrm_ea += _regs[base_reg];
+				}
+				switch (index_reg) {
+				case 4:
+					break;
+				default:
+					modrm_ea += _regs[index_reg] << scale;
+
+				}
+				break;
+			case 5:
+				if (modrm_mod != 0)
+					modrm_ea += _regs[modrm_rm];
+				else if (mode == X86EMUL_MODE_PROT64)
+					rip_relative = 1;
+				break;
+			default:
+				modrm_ea += _regs[modrm_rm];
+				break;
+			}
+			switch (modrm_mod) {
+			case 0:
+				if (modrm_rm == 5)
+					modrm_ea += insn_fetch(s32, 4, _eip);
+				break;
+			case 1:
+				modrm_ea += insn_fetch(s8, 1, _eip);
+				break;
+			case 2:
+				modrm_ea += insn_fetch(s32, 4, _eip);
+				break;
+			}
+		}
+		if (!override_base)
+			override_base = &ctxt->ds_base;
+		if (mode == X86EMUL_MODE_PROT64 &&
+		    override_base != &ctxt->fs_base &&
+		    override_base != &ctxt->gs_base)
+			override_base = 0;
+
+		if (override_base)
+			modrm_ea += *override_base;
+
+		if (rip_relative) {
+			modrm_ea += _eip;
+			switch (d & SrcMask) {
+			case SrcImmByte:
+				modrm_ea += 1;
+				break;
+			case SrcImm:
+				if (d & ByteOp)
+					modrm_ea += 1;
+				else
+					if (op_bytes == 8)
+						modrm_ea += 4;
+					else
+						modrm_ea += op_bytes;
+			}
+		}
+		if (ad_bytes != 8)
+			modrm_ea = (u32)modrm_ea;
+		cr2 = modrm_ea;
+	modrm_done:
+		;
+	}
+
+	/* Decode and fetch the destination operand: register or memory. */
+	switch (d & DstMask) {
+	case ImplicitOps:
+		/* Special instructions do their own operand decoding. */
+		goto special_insn;
+	case DstReg:
+		dst.type = OP_REG;
+		if ((d & ByteOp)
+		    && !(twobyte_table && (b == 0xb6 || b == 0xb7))) {
+			dst.ptr = decode_register(modrm_reg, _regs,
+						  (rex_prefix == 0));
+			dst.val = *(u8 *) dst.ptr;
+			dst.bytes = 1;
+		} else {
+			dst.ptr = decode_register(modrm_reg, _regs, 0);
+			switch ((dst.bytes = op_bytes)) {
+			case 2:
+				dst.val = *(u16 *)dst.ptr;
+				break;
+			case 4:
+				dst.val = *(u32 *)dst.ptr;
+				break;
+			case 8:
+				dst.val = *(u64 *)dst.ptr;
+				break;
+			}
+		}
+		break;
+	case DstMem:
+		dst.type = OP_MEM;
+		dst.ptr = (unsigned long *)cr2;
+		dst.bytes = (d & ByteOp) ? 1 : op_bytes;
+		if (!(d & Mov) && /* optimisation - avoid slow emulated read */
+		    ((rc = ops->read_emulated((unsigned long)dst.ptr,
+					      &dst.val, dst.bytes, ctxt)) != 0))
+			goto done;
+		break;
+	}
+	dst.orig_val = dst.val;
+
+	/*
+	 * Decode and fetch the source operand: register, memory
+	 * or immediate.
+	 */
+	switch (d & SrcMask) {
+	case SrcNone:
+		break;
+	case SrcReg:
+		src.type = OP_REG;
+		if (d & ByteOp) {
+			src.ptr = decode_register(modrm_reg, _regs,
+						  (rex_prefix == 0));
+			src.val = src.orig_val = *(u8 *) src.ptr;
+			src.bytes = 1;
+		} else {
+			src.ptr = decode_register(modrm_reg, _regs, 0);
+			switch ((src.bytes = op_bytes)) {
+			case 2:
+				src.val = src.orig_val = *(u16 *) src.ptr;
+				break;
+			case 4:
+				src.val = src.orig_val = *(u32 *) src.ptr;
+				break;
+			case 8:
+				src.val = src.orig_val = *(u64 *) src.ptr;
+				break;
+			}
+		}
+		break;
+	case SrcMem16:
+		src.bytes = 2;
+		goto srcmem_common;
+	case SrcMem32:
+		src.bytes = 4;
+		goto srcmem_common;
+	case SrcMem:
+		src.bytes = (d & ByteOp) ? 1 : op_bytes;
+	      srcmem_common:
+		src.type = OP_MEM;
+		src.ptr = (unsigned long *)cr2;
+		if ((rc = ops->read_emulated((unsigned long)src.ptr,
+					     &src.val, src.bytes, ctxt)) != 0)
+			goto done;
+		src.orig_val = src.val;
+		break;
+	case SrcImm:
+		src.type = OP_IMM;
+		src.ptr = (unsigned long *)_eip;
+		src.bytes = (d & ByteOp) ? 1 : op_bytes;
+		if (src.bytes == 8)
+			src.bytes = 4;
+		/* NB. Immediates are sign-extended as necessary. */
+		switch (src.bytes) {
+		case 1:
+			src.val = insn_fetch(s8, 1, _eip);
+			break;
+		case 2:
+			src.val = insn_fetch(s16, 2, _eip);
+			break;
+		case 4:
+			src.val = insn_fetch(s32, 4, _eip);
+			break;
+		}
+		break;
+	case SrcImmByte:
+		src.type = OP_IMM;
+		src.ptr = (unsigned long *)_eip;
+		src.bytes = 1;
+		src.val = insn_fetch(s8, 1, _eip);
+		break;
+	}
+
+	if (twobyte)
+		goto twobyte_insn;
+
+	switch (b) {
+	case 0x00 ... 0x05:
+	      add:		/* add */
+		emulate_2op_SrcV("add", src, dst, _eflags);
+		break;
+	case 0x08 ... 0x0d:
+	      or:		/* or */
+		emulate_2op_SrcV("or", src, dst, _eflags);
+		break;
+	case 0x10 ... 0x15:
+	      adc:		/* adc */
+		emulate_2op_SrcV("adc", src, dst, _eflags);
+		break;
+	case 0x18 ... 0x1d:
+	      sbb:		/* sbb */
+		emulate_2op_SrcV("sbb", src, dst, _eflags);
+		break;
+	case 0x20 ... 0x25:
+	      and:		/* and */
+		emulate_2op_SrcV("and", src, dst, _eflags);
+		break;
+	case 0x28 ... 0x2d:
+	      sub:		/* sub */
+		emulate_2op_SrcV("sub", src, dst, _eflags);
+		break;
+	case 0x30 ... 0x35:
+	      xor:		/* xor */
+		emulate_2op_SrcV("xor", src, dst, _eflags);
+		break;
+	case 0x38 ... 0x3d:
+	      cmp:		/* cmp */
+		emulate_2op_SrcV("cmp", src, dst, _eflags);
+		break;
+	case 0x63:		/* movsxd */
+		if (mode != X86EMUL_MODE_PROT64)
+			goto cannot_emulate;
+		dst.val = (s32) src.val;
+		break;
+	case 0x80 ... 0x83:	/* Grp1 */
+		switch (modrm_reg) {
+		case 0:
+			goto add;
+		case 1:
+			goto or;
+		case 2:
+			goto adc;
+		case 3:
+			goto sbb;
+		case 4:
+			goto and;
+		case 5:
+			goto sub;
+		case 6:
+			goto xor;
+		case 7:
+			goto cmp;
+		}
+		break;
+	case 0x84 ... 0x85:
+	      test:		/* test */
+		emulate_2op_SrcV("test", src, dst, _eflags);
+		break;
+	case 0x86 ... 0x87:	/* xchg */
+		/* Write back the register source. */
+		switch (dst.bytes) {
+		case 1:
+			*(u8 *) src.ptr = (u8) dst.val;
+			break;
+		case 2:
+			*(u16 *) src.ptr = (u16) dst.val;
+			break;
+		case 4:
+			*src.ptr = (u32) dst.val;
+			break;	/* 64b reg: zero-extend */
+		case 8:
+			*src.ptr = dst.val;
+			break;
+		}
+		/*
+		 * Write back the memory destination with implicit LOCK
+		 * prefix.
+		 */
+		dst.val = src.val;
+		lock_prefix = 1;
+		break;
+	case 0xa0 ... 0xa1:	/* mov */
+		dst.ptr = (unsigned long *)&_regs[VCPU_REGS_RAX];
+		dst.val = src.val;
+		_eip += ad_bytes;	/* skip src displacement */
+		break;
+	case 0xa2 ... 0xa3:	/* mov */
+		dst.val = (unsigned long)_regs[VCPU_REGS_RAX];
+		_eip += ad_bytes;	/* skip dst displacement */
+		break;
+	case 0x88 ... 0x8b:	/* mov */
+	case 0xc6 ... 0xc7:	/* mov (sole member of Grp11) */
+		dst.val = src.val;
+		break;
+	case 0x8f:		/* pop (sole member of Grp1a) */
+		/* 64-bit mode: POP always pops a 64-bit operand. */
+		if (mode == X86EMUL_MODE_PROT64)
+			dst.bytes = 8;
+		if ((rc = ops->read_std(register_address(ctxt->ss_base,
+							 _regs[VCPU_REGS_RSP]),
+					&dst.val, dst.bytes, ctxt)) != 0)
+			goto done;
+		register_address_increment(_regs[VCPU_REGS_RSP], dst.bytes);
+		break;
+	case 0xc0 ... 0xc1:
+	      grp2:		/* Grp2 */
+		switch (modrm_reg) {
+		case 0:	/* rol */
+			emulate_2op_SrcB("rol", src, dst, _eflags);
+			break;
+		case 1:	/* ror */
+			emulate_2op_SrcB("ror", src, dst, _eflags);
+			break;
+		case 2:	/* rcl */
+			emulate_2op_SrcB("rcl", src, dst, _eflags);
+			break;
+		case 3:	/* rcr */
+			emulate_2op_SrcB("rcr", src, dst, _eflags);
+			break;
+		case 4:	/* sal/shl */
+		case 6:	/* sal/shl */
+			emulate_2op_SrcB("sal", src, dst, _eflags);
+			break;
+		case 5:	/* shr */
+			emulate_2op_SrcB("shr", src, dst, _eflags);
+			break;
+		case 7:	/* sar */
+			emulate_2op_SrcB("sar", src, dst, _eflags);
+			break;
+		}
+		break;
+	case 0xd0 ... 0xd1:	/* Grp2 */
+		src.val = 1;
+		goto grp2;
+	case 0xd2 ... 0xd3:	/* Grp2 */
+		src.val = _regs[VCPU_REGS_RCX];
+		goto grp2;
+	case 0xf6 ... 0xf7:	/* Grp3 */
+		switch (modrm_reg) {
+		case 0 ... 1:	/* test */
+			/*
+			 * Special case in Grp3: test has an immediate
+			 * source operand.
+			 */
+			src.type = OP_IMM;
+			src.ptr = (unsigned long *)_eip;
+			src.bytes = (d & ByteOp) ? 1 : op_bytes;
+			if (src.bytes == 8)
+				src.bytes = 4;
+			switch (src.bytes) {
+			case 1:
+				src.val = insn_fetch(s8, 1, _eip);
+				break;
+			case 2:
+				src.val = insn_fetch(s16, 2, _eip);
+				break;
+			case 4:
+				src.val = insn_fetch(s32, 4, _eip);
+				break;
+			}
+			goto test;
+		case 2:	/* not */
+			dst.val = ~dst.val;
+			break;
+		case 3:	/* neg */
+			emulate_1op("neg", dst, _eflags);
+			break;
+		default:
+			goto cannot_emulate;
+		}
+		break;
+	case 0xfe ... 0xff:	/* Grp4/Grp5 */
+		switch (modrm_reg) {
+		case 0:	/* inc */
+			emulate_1op("inc", dst, _eflags);
+			break;
+		case 1:	/* dec */
+			emulate_1op("dec", dst, _eflags);
+			break;
+		case 6:	/* push */
+			/* 64-bit mode: PUSH always pushes a 64-bit operand. */
+			if (mode == X86EMUL_MODE_PROT64) {
+				dst.bytes = 8;
+				if ((rc = ops->read_std((unsigned long)dst.ptr,
+							&dst.val, 8,
+							ctxt)) != 0)
+					goto done;
+			}
+			register_address_increment(_regs[VCPU_REGS_RSP],
+						   -dst.bytes);
+			if ((rc = ops->write_std(
+				     register_address(ctxt->ss_base,
+						      _regs[VCPU_REGS_RSP]),
+				     dst.val, dst.bytes, ctxt)) != 0)
+				goto done;
+			dst.val = dst.orig_val;	/* skanky: disable writeback */
+			break;
+		default:
+			goto cannot_emulate;
+		}
+		break;
+	}
+
+writeback:
+	if ((d & Mov) || (dst.orig_val != dst.val)) {
+		switch (dst.type) {
+		case OP_REG:
+			/* The 4-byte case *is* correct: in 64-bit mode we zero-extend. */
+			switch (dst.bytes) {
+			case 1:
+				*(u8 *)dst.ptr = (u8)dst.val;
+				break;
+			case 2:
+				*(u16 *)dst.ptr = (u16)dst.val;
+				break;
+			case 4:
+				*dst.ptr = (u32)dst.val;
+				break;	/* 64b: zero-ext */
+			case 8:
+				*dst.ptr = dst.val;
+				break;
+			}
+			break;
+		case OP_MEM:
+			if (lock_prefix)
+				rc = ops->cmpxchg_emulated((unsigned long)dst.
+							   ptr, dst.orig_val,
+							   dst.val, dst.bytes,
+							   ctxt);
+			else
+				rc = ops->write_emulated((unsigned long)dst.ptr,
+							 dst.val, dst.bytes,
+							 ctxt);
+			if (rc != 0)
+				goto done;
+		default:
+			break;
+		}
+	}
+
+	/* Commit shadow register state. */
+	memcpy(ctxt->vcpu->regs, _regs, sizeof _regs);
+	ctxt->eflags = _eflags;
+	ctxt->vcpu->rip = _eip;
+
+done:
+	return (rc == X86EMUL_UNHANDLEABLE) ? -1 : 0;
+
+special_insn:
+	if (twobyte)
+		goto twobyte_special_insn;
+	if (rep_prefix) {
+		if (_regs[VCPU_REGS_RCX] == 0) {
+			ctxt->vcpu->rip = _eip;
+			goto done;
+		}
+		_regs[VCPU_REGS_RCX]--;
+		_eip = ctxt->vcpu->rip;
+	}
+	switch (b) {
+	case 0xa4 ... 0xa5:	/* movs */
+		dst.type = OP_MEM;
+		dst.bytes = (d & ByteOp) ? 1 : op_bytes;
+		dst.ptr = (unsigned long *)register_address(ctxt->es_base,
+							_regs[VCPU_REGS_RDI]);
+		if ((rc = ops->read_emulated(register_address(
+		      override_base ? *override_base : ctxt->ds_base,
+		      _regs[VCPU_REGS_RSI]), &dst.val, dst.bytes, ctxt)) != 0)
+			goto done;
+		register_address_increment(_regs[VCPU_REGS_RSI],
+			     (_eflags & EFLG_DF) ? -dst.bytes : dst.bytes);
+		register_address_increment(_regs[VCPU_REGS_RDI],
+			     (_eflags & EFLG_DF) ? -dst.bytes : dst.bytes);
+		break;
+	case 0xa6 ... 0xa7:	/* cmps */
+		DPRINTF("Urk! I don't handle CMPS.\n");
+		goto cannot_emulate;
+	case 0xaa ... 0xab:	/* stos */
+		dst.type = OP_MEM;
+		dst.bytes = (d & ByteOp) ? 1 : op_bytes;
+		dst.ptr = (unsigned long *)cr2;
+		dst.val = _regs[VCPU_REGS_RAX];
+		register_address_increment(_regs[VCPU_REGS_RDI],
+			     (_eflags & EFLG_DF) ? -dst.bytes : dst.bytes);
+		break;
+	case 0xac ... 0xad:	/* lods */
+		dst.type = OP_REG;
+		dst.bytes = (d & ByteOp) ? 1 : op_bytes;
+		dst.ptr = (unsigned long *)&_regs[VCPU_REGS_RAX];
+		if ((rc = ops->read_emulated(cr2, &dst.val, dst.bytes, ctxt)) != 0)
+			goto done;
+		register_address_increment(_regs[VCPU_REGS_RSI],
+			   (_eflags & EFLG_DF) ? -dst.bytes : dst.bytes);
+		break;
+	case 0xae ... 0xaf:	/* scas */
+		DPRINTF("Urk! I don't handle SCAS.\n");
+		goto cannot_emulate;
+	}
+	goto writeback;
+
+twobyte_insn:
+	switch (b) {
+	case 0x01: /* lgdt, lidt, lmsw */
+		switch (modrm_reg) {
+			u16 size;
+			unsigned long address;
+
+		case 2: /* lgdt */
+			rc = read_descriptor(ctxt, ops, src.ptr,
+					     &size, &address, op_bytes);
+			if (rc)
+				goto done;
+			realmode_lgdt(ctxt->vcpu, size, address);
+			break;
+		case 3: /* lidt */
+			rc = read_descriptor(ctxt, ops, src.ptr,
+					     &size, &address, op_bytes);
+			if (rc)
+				goto done;
+			realmode_lidt(ctxt->vcpu, size, address);
+			break;
+		case 6: /* lmsw */
+			realmode_lmsw(ctxt->vcpu, (u16)modrm_val, &_eflags);
+			break;
+		default:
+			goto cannot_emulate;
+		}
+		break;
+	case 0x40 ... 0x4f:	/* cmov */
+		dst.val = dst.orig_val = src.val;
+		d &= ~Mov;	/* default to no move */
+		/*
+		 * First, assume we're decoding an even cmov opcode
+		 * (lsb == 0).
+		 */
+		switch ((b & 15) >> 1) {
+		case 0:	/* cmovo */
+			d |= (_eflags & EFLG_OF) ? Mov : 0;
+			break;
+		case 1:	/* cmovb/cmovc/cmovnae */
+			d |= (_eflags & EFLG_CF) ? Mov : 0;
+			break;
+		case 2:	/* cmovz/cmove */
+			d |= (_eflags & EFLG_ZF) ? Mov : 0;
+			break;
+		case 3:	/* cmovbe/cmovna */
+			d |= (_eflags & (EFLG_CF | EFLG_ZF)) ? Mov : 0;
+			break;
+		case 4:	/* cmovs */
+			d |= (_eflags & EFLG_SF) ? Mov : 0;
+			break;
+		case 5:	/* cmovp/cmovpe */
+			d |= (_eflags & EFLG_PF) ? Mov : 0;
+			break;
+		case 7:	/* cmovle/cmovng */
+			d |= (_eflags & EFLG_ZF) ? Mov : 0;
+			/* fall through */
+		case 6:	/* cmovl/cmovnge */
+			d |= (!(_eflags & EFLG_SF) !=
+			      !(_eflags & EFLG_OF)) ? Mov : 0;
+			break;
+		}
+		/* Odd cmov opcodes (lsb == 1) have inverted sense. */
+		d ^= (b & 1) ? Mov : 0;
+		break;
+	case 0xb0 ... 0xb1:	/* cmpxchg */
+		/*
+		 * Save real source value, then compare EAX against
+		 * destination.
+		 */
+		src.orig_val = src.val;
+		src.val = _regs[VCPU_REGS_RAX];
+		emulate_2op_SrcV("cmp", src, dst, _eflags);
+		/* Always write back. The question is: where to? */
+		d |= Mov;
+		if (_eflags & EFLG_ZF) {
+			/* Success: write back to memory. */
+			dst.val = src.orig_val;
+		} else {
+			/* Failure: write the value we saw to EAX. */
+			dst.type = OP_REG;
+			dst.ptr = (unsigned long *)&_regs[VCPU_REGS_RAX];
+		}
+		break;
+	case 0xa3:
+	      bt:		/* bt */
+		src.val &= (dst.bytes << 3) - 1; /* only subword offset */
+		emulate_2op_SrcV_nobyte("bt", src, dst, _eflags);
+		break;
+	case 0xb3:
+	      btr:		/* btr */
+		src.val &= (dst.bytes << 3) - 1; /* only subword offset */
+		emulate_2op_SrcV_nobyte("btr", src, dst, _eflags);
+		break;
+	case 0xab:
+	      bts:		/* bts */
+		src.val &= (dst.bytes << 3) - 1; /* only subword offset */
+		emulate_2op_SrcV_nobyte("bts", src, dst, _eflags);
+		break;
+	case 0xb6 ... 0xb7:	/* movzx */
+		dst.bytes = op_bytes;
+		dst.val = (d & ByteOp) ? (u8) src.val : (u16) src.val;
+		break;
+	case 0xbb:
+	      btc:		/* btc */
+		src.val &= (dst.bytes << 3) - 1; /* only subword offset */
+		emulate_2op_SrcV_nobyte("btc", src, dst, _eflags);
+		break;
+	case 0xba:		/* Grp8 */
+		switch (modrm_reg & 3) {
+		case 0:
+			goto bt;
+		case 1:
+			goto bts;
+		case 2:
+			goto btr;
+		case 3:
+			goto btc;
+		}
+		break;
+	case 0xbe ... 0xbf:	/* movsx */
+		dst.bytes = op_bytes;
+		dst.val = (d & ByteOp) ? (s8) src.val : (s16) src.val;
+		break;
+	}
+	goto writeback;
+
+twobyte_special_insn:
+	/* Disable writeback. */
+	dst.orig_val = dst.val;
+	switch (b) {
+	case 0x0d:		/* GrpP (prefetch) */
+	case 0x18:		/* Grp16 (prefetch/nop) */
+		break;
+	case 0x20: /* mov cr, reg */
+		b = insn_fetch(u8, 1, _eip);
+		if ((b & 0xc0) != 0xc0)
+			goto cannot_emulate;
+		_regs[(b >> 3) & 7] = realmode_get_cr(ctxt->vcpu, b & 7);
+		break;
+	case 0x22: /* mov reg, cr */
+		b = insn_fetch(u8, 1, _eip);
+		if ((b & 0xc0) != 0xc0)
+			goto cannot_emulate;
+		realmode_set_cr(ctxt->vcpu, b & 7, _regs[(b >> 3) & 7] & -1u,
+				&_eflags);
+		break;
+	case 0xc7:		/* Grp9 (cmpxchg8b) */
+#if defined(__i386__)
+		{
+			unsigned long old_lo, old_hi;
+			if (((rc = ops->read_emulated(cr2 + 0, &old_lo, 4,
+						      ctxt)) != 0)
+			    || ((rc = ops->read_emulated(cr2 + 4, &old_hi, 4,
+							 ctxt)) != 0))
+				goto done;
+			if ((old_lo != _regs[VCPU_REGS_RAX])
+			    || (old_hi != _regs[VCPU_REGS_RDI])) {
+				_regs[VCPU_REGS_RAX] = old_lo;
+				_regs[VCPU_REGS_RDX] = old_hi;
+				_eflags &= ~EFLG_ZF;
+			} else if (ops->cmpxchg8b_emulated == NULL) {
+				rc = X86EMUL_UNHANDLEABLE;
+				goto done;
+			} else {
+				if ((rc = ops->cmpxchg8b_emulated(cr2, old_lo,
+							  old_hi,
+							  _regs[VCPU_REGS_RBX],
+							  _regs[VCPU_REGS_RCX],
+							  ctxt)) != 0)
+					goto done;
+				_eflags |= EFLG_ZF;
+			}
+			break;
+		}
+#elif defined(__x86_64__)
+		{
+			unsigned long old, new;
+			if ((rc = ops->read_emulated(cr2, &old, 8, ctxt)) != 0)
+				goto done;
+			if (((u32) (old >> 0) != (u32) _regs[VCPU_REGS_RAX]) ||
+			    ((u32) (old >> 32) != (u32) _regs[VCPU_REGS_RDX])) {
+				_regs[VCPU_REGS_RAX] = (u32) (old >> 0);
+				_regs[VCPU_REGS_RDX] = (u32) (old >> 32);
+				_eflags &= ~EFLG_ZF;
+			} else {
+				new = (_regs[VCPU_REGS_RCX] << 32) | (u32) _regs[VCPU_REGS_RBX];
+				if ((rc = ops->cmpxchg_emulated(cr2, old,
+							  new, 8, ctxt)) != 0)
+					goto done;
+				_eflags |= EFLG_ZF;
+			}
+			break;
+		}
+#endif
+	}
+	goto writeback;
+
+cannot_emulate:
+	DPRINTF("Cannot emulate %02x\n", b);
+	return -1;
+}
+
+#ifdef __XEN__
+
+#include <asm/mm.h>
+#include <asm/uaccess.h>
+
+int
+x86_emulate_read_std(unsigned long addr,
+		     unsigned long *val,
+		     unsigned int bytes, struct x86_emulate_ctxt *ctxt)
+{
+	unsigned int rc;
+
+	*val = 0;
+
+	if ((rc = copy_from_user((void *)val, (void *)addr, bytes)) != 0) {
+		propagate_page_fault(addr + bytes - rc, 0);	/* read fault */
+		return X86EMUL_PROPAGATE_FAULT;
+	}
+
+	return X86EMUL_CONTINUE;
+}
+
+int
+x86_emulate_write_std(unsigned long addr,
+		      unsigned long val,
+		      unsigned int bytes, struct x86_emulate_ctxt *ctxt)
+{
+	unsigned int rc;
+
+	if ((rc = copy_to_user((void *)addr, (void *)&val, bytes)) != 0) {
+		propagate_page_fault(addr + bytes - rc, PGERR_write_access);
+		return X86EMUL_PROPAGATE_FAULT;
+	}
+
+	return X86EMUL_CONTINUE;
+}
+
+#endif
Index: linux-2.6/drivers/kvm/x86_emulate.h
===================================================================
--- /dev/null
+++ linux-2.6/drivers/kvm/x86_emulate.h
@@ -0,0 +1,185 @@
+/******************************************************************************
+ * x86_emulate.h
+ *
+ * Generic x86 (32-bit and 64-bit) instruction decoder and emulator.
+ *
+ * Copyright (c) 2005 Keir Fraser
+ *
+ * From: xen-unstable 10676:af9809f51f81a3c43f276f00c81a52ef558afda4
+ */
+
+#ifndef __X86_EMULATE_H__
+#define __X86_EMULATE_H__
+
+struct x86_emulate_ctxt;
+
+/*
+ * x86_emulate_ops:
+ *
+ * These operations represent the instruction emulator's interface to memory.
+ * There are two categories of operation: those that act on ordinary memory
+ * regions (*_std), and those that act on memory regions known to require
+ * special treatment or emulation (*_emulated).
+ *
+ * The emulator assumes that an instruction accesses only one 'emulated memory'
+ * location, that this location is the given linear faulting address (cr2), and
+ * that this is one of the instruction's data operands. Instruction fetches and
+ * stack operations are assumed never to access emulated memory. The emulator
+ * automatically deduces which operand of a string-move operation is accessing
+ * emulated memory, and assumes that the other operand accesses normal memory.
+ *
+ * NOTES:
+ *  1. The emulator isn't very smart about emulated vs. standard memory.
+ *     'Emulated memory' access addresses should be checked for sanity.
+ *     'Normal memory' accesses may fault, and the caller must arrange to
+ *     detect and handle reentrancy into the emulator via recursive faults.
+ *     Accesses may be unaligned and may cross page boundaries.
+ *  2. If the access fails (cannot emulate, or a standard access faults) then
+ *     it is up to the memop to propagate the fault to the guest VM via
+ *     some out-of-band mechanism, unknown to the emulator. The memop signals
+ *     failure by returning X86EMUL_PROPAGATE_FAULT to the emulator, which will
+ *     then immediately bail.
+ *  3. Valid access sizes are 1, 2, 4 and 8 bytes. On x86/32 systems only
+ *     cmpxchg8b_emulated need support 8-byte accesses.
+ *  4. The emulator cannot handle 64-bit mode emulation on an x86/32 system.
+ */
+/* Access completed successfully: continue emulation as normal. */
+#define X86EMUL_CONTINUE        0
+/* Access is unhandleable: bail from emulation and return error to caller. */
+#define X86EMUL_UNHANDLEABLE    1
+/* Terminate emulation but return success to the caller. */
+#define X86EMUL_PROPAGATE_FAULT 2 /* propagate a generated fault to guest */
+#define X86EMUL_RETRY_INSTR     2 /* retry the instruction for some reason */
+#define X86EMUL_CMPXCHG_FAILED  2 /* cmpxchg did not see expected value */
+struct x86_emulate_ops {
+	/*
+	 * read_std: Read bytes of standard (non-emulated/special) memory.
+	 *           Used for instruction fetch, stack operations, and others.
+	 *  @addr:  [IN ] Linear address from which to read.
+	 *  @val:   [OUT] Value read from memory, zero-extended to 'u_long'.
+	 *  @bytes: [IN ] Number of bytes to read from memory.
+	 */
+	int (*read_std)(unsigned long addr,
+			unsigned long *val,
+			unsigned int bytes, struct x86_emulate_ctxt * ctxt);
+
+	/*
+	 * write_std: Write bytes of standard (non-emulated/special) memory.
+	 *            Used for stack operations, and others.
+	 *  @addr:  [IN ] Linear address to which to write.
+	 *  @val:   [IN ] Value to write to memory (low-order bytes used as
+	 *                required).
+	 *  @bytes: [IN ] Number of bytes to write to memory.
+	 */
+	int (*write_std)(unsigned long addr,
+			 unsigned long val,
+			 unsigned int bytes, struct x86_emulate_ctxt * ctxt);
+
+	/*
+	 * read_emulated: Read bytes from emulated/special memory area.
+	 *  @addr:  [IN ] Linear address from which to read.
+	 *  @val:   [OUT] Value read from memory, zero-extended to 'u_long'.
+	 *  @bytes: [IN ] Number of bytes to read from memory.
+	 */
+	int (*read_emulated) (unsigned long addr,
+			      unsigned long *val,
+			      unsigned int bytes,
+			      struct x86_emulate_ctxt * ctxt);
+
+	/*
+	 * write_emulated: Read bytes from emulated/special memory area.
+	 *  @addr:  [IN ] Linear address to which to write.
+	 *  @val:   [IN ] Value to write to memory (low-order bytes used as
+	 *                required).
+	 *  @bytes: [IN ] Number of bytes to write to memory.
+	 */
+	int (*write_emulated) (unsigned long addr,
+			       unsigned long val,
+			       unsigned int bytes,
+			       struct x86_emulate_ctxt * ctxt);
+
+	/*
+	 * cmpxchg_emulated: Emulate an atomic (LOCKed) CMPXCHG operation on an
+	 *                   emulated/special memory area.
+	 *  @addr:  [IN ] Linear address to access.
+	 *  @old:   [IN ] Value expected to be current at @addr.
+	 *  @new:   [IN ] Value to write to @addr.
+	 *  @bytes: [IN ] Number of bytes to access using CMPXCHG.
+	 */
+	int (*cmpxchg_emulated) (unsigned long addr,
+				 unsigned long old,
+				 unsigned long new,
+				 unsigned int bytes,
+				 struct x86_emulate_ctxt * ctxt);
+
+	/*
+	 * cmpxchg8b_emulated: Emulate an atomic (LOCKed) CMPXCHG8B operation on an
+	 *                     emulated/special memory area.
+	 *  @addr:  [IN ] Linear address to access.
+	 *  @old:   [IN ] Value expected to be current at @addr.
+	 *  @new:   [IN ] Value to write to @addr.
+	 * NOTES:
+	 *  1. This function is only ever called when emulating a real CMPXCHG8B.
+	 *  2. This function is *never* called on x86/64 systems.
+	 *  2. Not defining this function (i.e., specifying NULL) is equivalent
+	 *     to defining a function that always returns X86EMUL_UNHANDLEABLE.
+	 */
+	int (*cmpxchg8b_emulated) (unsigned long addr,
+				   unsigned long old_lo,
+				   unsigned long old_hi,
+				   unsigned long new_lo,
+				   unsigned long new_hi,
+				   struct x86_emulate_ctxt * ctxt);
+};
+
+struct cpu_user_regs;
+
+struct x86_emulate_ctxt {
+	/* Register state before/after emulation. */
+	struct kvm_vcpu *vcpu;
+
+	/* Linear faulting address (if emulating a page-faulting instruction). */
+	unsigned long eflags;
+	unsigned long cr2;
+
+	/* Emulated execution mode, represented by an X86EMUL_MODE value. */
+	int mode;
+
+	unsigned long cs_base;
+	unsigned long ds_base;
+	unsigned long es_base;
+	unsigned long ss_base;
+	unsigned long gs_base;
+	unsigned long fs_base;
+};
+
+/* Execution mode, passed to the emulator. */
+#define X86EMUL_MODE_REAL     0	/* Real mode.             */
+#define X86EMUL_MODE_PROT16   2	/* 16-bit protected mode. */
+#define X86EMUL_MODE_PROT32   4	/* 32-bit protected mode. */
+#define X86EMUL_MODE_PROT64   8	/* 64-bit (long) mode.    */
+
+/* Host execution mode. */
+#if defined(__i386__)
+#define X86EMUL_MODE_HOST X86EMUL_MODE_PROT32
+#elif defined(__x86_64__)
+#define X86EMUL_MODE_HOST X86EMUL_MODE_PROT64
+#endif
+
+/*
+ * x86_emulate_memop: Emulate an instruction that faulted attempting to
+ *                    read/write a 'special' memory area.
+ * Returns -1 on failure, 0 on success.
+ */
+int x86_emulate_memop(struct x86_emulate_ctxt *ctxt,
+		      struct x86_emulate_ops *ops);
+
+/*
+ * Given the 'reg' portion of a ModRM byte, and a register block, return a
+ * pointer into the block that addresses the relevant register.
+ * @highbyte_regs specifies whether to decode AH,CH,DH,BH.
+ */
+void *decode_register(u8 modrm_reg, unsigned long *regs,
+		      int highbyte_regs);
+
+#endif				/* __X86_EMULATE_H__ */
-
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