KVM: x86: tag the instructions which are used to write page table

The idea is from Avi:
| tag instructions that are typically used to modify the page tables, and
| drop shadow if any other instruction is used.
| The list would include, I'd guess, and, or, bts, btc, mov, xchg, cmpxchg,
| and cmpxchg8b.

This patch is used to tag the instructions and in the later path, shadow page
is dropped if it is written by other instructions

Signed-off-by: Xiao Guangrong <[email protected]>
Signed-off-by: Avi Kivity <[email protected]>

Author: Xiao Guangrong

arch/x86/kvm/emulate.c

@@ -125,8 +125,9 @@
 #define Lock        (1<<26) /* lock prefix is allowed for the instruction */
 #define Priv        (1<<27) /* instruction generates #GP if current CPL != 0 */
 #define No64	    (1<<28)
+#define PageTable   (1 << 29)   /* instruction used to write page table */
 /* Source 2 operand type */
-#define Src2Shift   (29)
+#define Src2Shift   (30)
 #define Src2None    (OpNone << Src2Shift)
 #define Src2CL      (OpCL << Src2Shift)
 #define Src2ImmByte (OpImmByte << Src2Shift)
@@ -3033,10 +3034,10 @@ static struct opcode group7_rm7[] = {
 
 static struct opcode group1[] = {
 	I(Lock, em_add),
-	I(Lock, em_or),
+	I(Lock | PageTable, em_or),
 	I(Lock, em_adc),
 	I(Lock, em_sbb),
-	I(Lock, em_and),
+	I(Lock | PageTable, em_and),
 	I(Lock, em_sub),
 	I(Lock, em_xor),
 	I(0, em_cmp),
@@ -3096,18 +3097,21 @@ static struct group_dual group7 = { {
 
 static struct opcode group8[] = {
 	N, N, N, N,
-	D(DstMem | SrcImmByte | ModRM), D(DstMem | SrcImmByte | ModRM | Lock),
-	D(DstMem | SrcImmByte | ModRM | Lock), D(DstMem | SrcImmByte | ModRM | Lock),
+	D(DstMem | SrcImmByte | ModRM),
+	D(DstMem | SrcImmByte | ModRM | Lock | PageTable),
+	D(DstMem | SrcImmByte | ModRM | Lock),
+	D(DstMem | SrcImmByte | ModRM | Lock | PageTable),
 };
 
 static struct group_dual group9 = { {
-	N, D(DstMem64 | ModRM | Lock), N, N, N, N, N, N,
+	N, D(DstMem64 | ModRM | Lock | PageTable), N, N, N, N, N, N,
 }, {
 	N, N, N, N, N, N, N, N,
 } };
 
 static struct opcode group11[] = {
-	I(DstMem | SrcImm | ModRM | Mov, em_mov), X7(D(Undefined)),
+	I(DstMem | SrcImm | ModRM | Mov | PageTable, em_mov),
+	X7(D(Undefined)),
 };
 
 static struct gprefix pfx_0f_6f_0f_7f = {
@@ -3120,7 +3124,7 @@ static struct opcode opcode_table[256] = {
 	I(ImplicitOps | Stack | No64 | Src2ES, em_push_sreg),
 	I(ImplicitOps | Stack | No64 | Src2ES, em_pop_sreg),
 	/* 0x08 - 0x0F */
-	I6ALU(Lock, em_or),
+	I6ALU(Lock | PageTable, em_or),
 	I(ImplicitOps | Stack | No64 | Src2CS, em_push_sreg),
 	N,
 	/* 0x10 - 0x17 */
@@ -3132,7 +3136,7 @@ static struct opcode opcode_table[256] = {
 	I(ImplicitOps | Stack | No64 | Src2DS, em_push_sreg),
 	I(ImplicitOps | Stack | No64 | Src2DS, em_pop_sreg),
 	/* 0x20 - 0x27 */
-	I6ALU(Lock, em_and), N, N,
+	I6ALU(Lock | PageTable, em_and), N, N,
 	/* 0x28 - 0x2F */
 	I6ALU(Lock, em_sub), N, I(ByteOp | DstAcc | No64, em_das),
 	/* 0x30 - 0x37 */
@@ -3165,11 +3169,11 @@ static struct opcode opcode_table[256] = {
 	G(ByteOp | DstMem | SrcImm | ModRM | No64 | Group, group1),
 	G(DstMem | SrcImmByte | ModRM | Group, group1),
 	I2bv(DstMem | SrcReg | ModRM, em_test),
-	I2bv(DstMem | SrcReg | ModRM | Lock, em_xchg),
+	I2bv(DstMem | SrcReg | ModRM | Lock | PageTable, em_xchg),
 	/* 0x88 - 0x8F */
-	I2bv(DstMem | SrcReg | ModRM | Mov, em_mov),
+	I2bv(DstMem | SrcReg | ModRM | Mov | PageTable, em_mov),
 	I2bv(DstReg | SrcMem | ModRM | Mov, em_mov),
-	I(DstMem | SrcNone | ModRM | Mov, em_mov_rm_sreg),
+	I(DstMem | SrcNone | ModRM | Mov | PageTable, em_mov_rm_sreg),
 	D(ModRM | SrcMem | NoAccess | DstReg),
 	I(ImplicitOps | SrcMem16 | ModRM, em_mov_sreg_rm),
 	G(0, group1A),
@@ -3182,7 +3186,7 @@ static struct opcode opcode_table[256] = {
 	II(ImplicitOps | Stack, em_popf, popf), N, N,
 	/* 0xA0 - 0xA7 */
 	I2bv(DstAcc | SrcMem | Mov | MemAbs, em_mov),
-	I2bv(DstMem | SrcAcc | Mov | MemAbs, em_mov),
+	I2bv(DstMem | SrcAcc | Mov | MemAbs | PageTable, em_mov),
 	I2bv(SrcSI | DstDI | Mov | String, em_mov),
 	I2bv(SrcSI | DstDI | String, em_cmp),
 	/* 0xA8 - 0xAF */
@@ -3280,20 +3284,21 @@ static struct opcode twobyte_table[256] = {
 	D(DstMem | SrcReg | Src2CL | ModRM), N, N,
 	/* 0xA8 - 0xAF */
 	I(Stack | Src2GS, em_push_sreg), I(Stack | Src2GS, em_pop_sreg),
-	DI(ImplicitOps, rsm), D(DstMem | SrcReg | ModRM | BitOp | Lock),
+	DI(ImplicitOps, rsm),
+	D(DstMem | SrcReg | ModRM | BitOp | Lock | PageTable),
 	D(DstMem | SrcReg | Src2ImmByte | ModRM),
 	D(DstMem | SrcReg | Src2CL | ModRM),
 	D(ModRM), I(DstReg | SrcMem | ModRM, em_imul),
 	/* 0xB0 - 0xB7 */
-	D2bv(DstMem | SrcReg | ModRM | Lock),
+	D2bv(DstMem | SrcReg | ModRM | Lock | PageTable),
 	I(DstReg | SrcMemFAddr | ModRM | Src2SS, em_lseg),
 	D(DstMem | SrcReg | ModRM | BitOp | Lock),
 	I(DstReg | SrcMemFAddr | ModRM | Src2FS, em_lseg),
 	I(DstReg | SrcMemFAddr | ModRM | Src2GS, em_lseg),
 	D(ByteOp | DstReg | SrcMem | ModRM | Mov), D(DstReg | SrcMem16 | ModRM | Mov),
 	/* 0xB8 - 0xBF */
 	N, N,
-	G(BitOp, group8), D(DstMem | SrcReg | ModRM | BitOp | Lock),
+	G(BitOp, group8), D(DstMem | SrcReg | ModRM | BitOp | Lock | PageTable),
 	D(DstReg | SrcMem | ModRM), D(DstReg | SrcMem | ModRM),
 	D(ByteOp | DstReg | SrcMem | ModRM | Mov), D(DstReg | SrcMem16 | ModRM | Mov),
 	/* 0xC0 - 0xCF */