KVM: x86 emulator: Use ctxt->_eip directly in do_insn_fetch_byte()

Instead of passing ctxt->_eip from insn_fetch() call sites, get it from
ctxt in do_insn_fetch_byte().  This is done by replacing the argument
_eip of insn_fetch() with _ctxt, which should be better than letting the
macro use ctxt silently in its body.

Though this changes the place where ctxt->_eip is incremented from
insn_fetch() to do_insn_fetch_byte(), this does not have any real
effect.
Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/x86/kvm/emulate.c

@@ -651,18 +651,26 @@ static int segmented_read_std(struct x86_emulate_ctxt *ctxt,
 	return ctxt->ops->read_std(ctxt, linear, data, size, &ctxt->exception);
 }
 
-static int do_insn_fetch_byte(struct x86_emulate_ctxt *ctxt,
-			      unsigned long eip, u8 *dest)
+/*
+ * Fetch the next byte of the instruction being emulated which is pointed to
+ * by ctxt->_eip, then increment ctxt->_eip.
+ *
+ * Also prefetch the remaining bytes of the instruction without crossing page
+ * boundary if they are not in fetch_cache yet.
+ */
+static int do_insn_fetch_byte(struct x86_emulate_ctxt *ctxt, u8 *dest)
 {
 	struct fetch_cache *fc = &ctxt->fetch;
 	int rc;
 	int size, cur_size;
 
-	if (eip == fc->end) {
+	if (ctxt->_eip == fc->end) {
 		unsigned long linear;
-		struct segmented_address addr = { .seg=VCPU_SREG_CS, .ea=eip};
+		struct segmented_address addr = { .seg = VCPU_SREG_CS,
+						  .ea  = ctxt->_eip };
 		cur_size = fc->end - fc->start;
-		size = min(15UL - cur_size, PAGE_SIZE - offset_in_page(eip));
+		size = min(15UL - cur_size,
+			   PAGE_SIZE - offset_in_page(ctxt->_eip));
 		rc = __linearize(ctxt, addr, size, false, true, &linear);
 		if (rc != X86EMUL_CONTINUE)
 			return rc;
@@ -672,20 +680,21 @@ static int do_insn_fetch_byte(struct x86_emulate_ctxt *ctxt,
 			return rc;
 		fc->end += size;
 	}
-	*dest = fc->data[eip - fc->start];
+	*dest = fc->data[ctxt->_eip - fc->start];
+	ctxt->_eip++;
 	return X86EMUL_CONTINUE;
 }
 
 static int do_insn_fetch(struct x86_emulate_ctxt *ctxt,
-			 unsigned long eip, void *dest, unsigned size)
+			 void *dest, unsigned size)
 {
 	int rc;
 
 	/* x86 instructions are limited to 15 bytes. */
-	if (eip + size - ctxt->eip > 15)
+	if (ctxt->_eip + size - ctxt->eip > 15)
 		return X86EMUL_UNHANDLEABLE;
 	while (size--) {
-		rc = do_insn_fetch_byte(ctxt, eip++, dest++);
+		rc = do_insn_fetch_byte(ctxt, dest++);
 		if (rc != X86EMUL_CONTINUE)
 			return rc;
 	}
@@ -693,20 +702,18 @@ static int do_insn_fetch(struct x86_emulate_ctxt *ctxt,
 }
 
 /* Fetch next part of the instruction being emulated. */
-#define insn_fetch(_type, _size, _eip)					\
+#define insn_fetch(_type, _size, _ctxt)					\
 ({	unsigned long _x;						\
-	rc = do_insn_fetch(ctxt, (_eip), &_x, (_size));			\
+	rc = do_insn_fetch(_ctxt, &_x, (_size));			\
 	if (rc != X86EMUL_CONTINUE)					\
 		goto done;						\
-	(_eip) += (_size);						\
 	(_type)_x;							\
 })
 
-#define insn_fetch_arr(_arr, _size, _eip)				\
-({	rc = do_insn_fetch(ctxt, (_eip), _arr, (_size));		\
+#define insn_fetch_arr(_arr, _size, _ctxt)				\
+({	rc = do_insn_fetch(_ctxt, _arr, (_size));			\
 	if (rc != X86EMUL_CONTINUE)					\
 		goto done;						\
-	(_eip) += (_size);						\
 })
 
 /*
@@ -894,7 +901,7 @@ 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, 1, ctxt->_eip);
+	ctxt->modrm = insn_fetch(u8, 1, ctxt);
 	ctxt->modrm_mod |= (ctxt->modrm & 0xc0) >> 6;
 	ctxt->modrm_reg |= (ctxt->modrm & 0x38) >> 3;
 	ctxt->modrm_rm |= (ctxt->modrm & 0x07);
@@ -928,13 +935,13 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt,
 		switch (ctxt->modrm_mod) {
 		case 0:
 			if (ctxt->modrm_rm == 6)
-				modrm_ea += insn_fetch(u16, 2, ctxt->_eip);
+				modrm_ea += insn_fetch(u16, 2, ctxt);
 			break;
 		case 1:
-			modrm_ea += insn_fetch(s8, 1, ctxt->_eip);
+			modrm_ea += insn_fetch(s8, 1, ctxt);
 			break;
 		case 2:
-			modrm_ea += insn_fetch(u16, 2, ctxt->_eip);
+			modrm_ea += insn_fetch(u16, 2, ctxt);
 			break;
 		}
 		switch (ctxt->modrm_rm) {
@@ -971,13 +978,13 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt,
 	} else {
 		/* 32/64-bit ModR/M decode. */
 		if ((ctxt->modrm_rm & 7) == 4) {
-			sib = insn_fetch(u8, 1, ctxt->_eip);
+			sib = insn_fetch(u8, 1, ctxt);
 			index_reg |= (sib >> 3) & 7;
 			base_reg |= sib & 7;
 			scale = sib >> 6;
 
 			if ((base_reg & 7) == 5 && ctxt->modrm_mod == 0)
-				modrm_ea += insn_fetch(s32, 4, ctxt->_eip);
+				modrm_ea += insn_fetch(s32, 4, ctxt);
 			else
 				modrm_ea += ctxt->regs[base_reg];
 			if (index_reg != 4)
@@ -990,13 +997,13 @@ static int decode_modrm(struct x86_emulate_ctxt *ctxt,
 		switch (ctxt->modrm_mod) {
 		case 0:
 			if (ctxt->modrm_rm == 5)
-				modrm_ea += insn_fetch(s32, 4, ctxt->_eip);
+				modrm_ea += insn_fetch(s32, 4, ctxt);
 			break;
 		case 1:
-			modrm_ea += insn_fetch(s8, 1, ctxt->_eip);
+			modrm_ea += insn_fetch(s8, 1, ctxt);
 			break;
 		case 2:
-			modrm_ea += insn_fetch(s32, 4, ctxt->_eip);
+			modrm_ea += insn_fetch(s32, 4, ctxt);
 			break;
 		}
 	}
@@ -1013,13 +1020,13 @@ static int decode_abs(struct x86_emulate_ctxt *ctxt,
 	op->type = OP_MEM;
 	switch (ctxt->ad_bytes) {
 	case 2:
-		op->addr.mem.ea = insn_fetch(u16, 2, ctxt->_eip);
+		op->addr.mem.ea = insn_fetch(u16, 2, ctxt);
 		break;
 	case 4:
-		op->addr.mem.ea = insn_fetch(u32, 4, ctxt->_eip);
+		op->addr.mem.ea = insn_fetch(u32, 4, ctxt);
 		break;
 	case 8:
-		op->addr.mem.ea = insn_fetch(u64, 8, ctxt->_eip);
+		op->addr.mem.ea = insn_fetch(u64, 8, ctxt);
 		break;
 	}
 done:
@@ -3309,13 +3316,13 @@ static int decode_imm(struct x86_emulate_ctxt *ctxt, struct operand *op,
 	/* NB. Immediates are sign-extended as necessary. */
 	switch (op->bytes) {
 	case 1:
-		op->val = insn_fetch(s8, 1, ctxt->_eip);
+		op->val = insn_fetch(s8, 1, ctxt);
 		break;
 	case 2:
-		op->val = insn_fetch(s16, 2, ctxt->_eip);
+		op->val = insn_fetch(s16, 2, ctxt);
 		break;
 	case 4:
-		op->val = insn_fetch(s32, 4, ctxt->_eip);
+		op->val = insn_fetch(s32, 4, ctxt);
 		break;
 	}
 	if (!sign_extension) {
@@ -3374,7 +3381,7 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len)
 
 	/* Legacy prefixes. */
 	for (;;) {
-		switch (ctxt->b = insn_fetch(u8, 1, ctxt->_eip)) {
+		switch (ctxt->b = insn_fetch(u8, 1, ctxt)) {
 		case 0x66:	/* operand-size override */
 			op_prefix = true;
 			/* switch between 2/4 bytes */
@@ -3430,7 +3437,7 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len)
 	/* Two-byte opcode? */
 	if (ctxt->b == 0x0f) {
 		ctxt->twobyte = 1;
-		ctxt->b = insn_fetch(u8, 1, ctxt->_eip);
+		ctxt->b = insn_fetch(u8, 1, ctxt);
 		opcode = twobyte_table[ctxt->b];
 	}
 	ctxt->d = opcode.flags;
@@ -3438,13 +3445,13 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len)
 	while (ctxt->d & GroupMask) {
 		switch (ctxt->d & GroupMask) {
 		case Group:
-			ctxt->modrm = insn_fetch(u8, 1, ctxt->_eip);
+			ctxt->modrm = insn_fetch(u8, 1, ctxt);
 			--ctxt->_eip;
 			goffset = (ctxt->modrm >> 3) & 7;
 			opcode = opcode.u.group[goffset];
 			break;
 		case GroupDual:
-			ctxt->modrm = insn_fetch(u8, 1, ctxt->_eip);
+			ctxt->modrm = insn_fetch(u8, 1, ctxt);
 			--ctxt->_eip;
 			goffset = (ctxt->modrm >> 3) & 7;
 			if ((ctxt->modrm >> 6) == 3)
@@ -3577,7 +3584,7 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len)
 		ctxt->src.type = OP_IMM;
 		ctxt->src.addr.mem.ea = ctxt->_eip;
 		ctxt->src.bytes = ctxt->op_bytes + 2;
-		insn_fetch_arr(ctxt->src.valptr, ctxt->src.bytes, ctxt->_eip);
+		insn_fetch_arr(ctxt->src.valptr, ctxt->src.bytes, ctxt);
 		break;
 	case SrcMemFAddr:
 		memop.bytes = ctxt->op_bytes + 2;
@@ -3630,7 +3637,7 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len)
 		ctxt->dst.type = OP_IMM;
 		ctxt->dst.addr.mem.ea = ctxt->_eip;
 		ctxt->dst.bytes = 1;
-		ctxt->dst.val = insn_fetch(u8, 1, ctxt->_eip);
+		ctxt->dst.val = insn_fetch(u8, 1, ctxt);
 		break;
 	case DstMem:
 	case DstMem64: