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Commit fb32b1ed authored by Avi Kivity's avatar Avi Kivity Committed by Gleb Natapov
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KVM: x86 emulator: add support for writing back the source operand 



Some instructions write back the source operand, not just the destination.
Add support for doing this via the decode flags.

Gleb: add BUG_ON() to prevent source to be memory operand.

Signed-off-by: default avatarAvi Kivity <avi.kivity@gmail.com>
Signed-off-by: default avatarGleb Natapov <gleb@redhat.com>
parent f8b5ff2c

arch/x86/kvm/emulate.c

+27 −21
Original line number Diff line number Diff line
@@ -155,6 +155,7 @@ 
#define Avx         ((u64)1 << 43)  /* Advanced Vector Extensions */

#define Fastop      ((u64)1 << 44)  /* Use opcode::u.fastop */

#define NoWrite     ((u64)1 << 45)  /* No writeback */

#define SrcWrite    ((u64)1 << 46)  /* Write back src operand */



#define X2(x...) x, x

#define X3(x...) X2(x), x
@@ -1723,45 +1724,42 @@ static void write_register_operand(struct operand *op) 
	}

}



static int writeback(struct x86_emulate_ctxt *ctxt)

static int writeback(struct x86_emulate_ctxt *ctxt, struct operand *op)

{

	int rc;



	if (ctxt->d & NoWrite)

		return X86EMUL_CONTINUE;



	switch (ctxt->dst.type) {

	switch (op->type) {

	case OP_REG:

		write_register_operand(&ctxt->dst);

		write_register_operand(op);

		break;

	case OP_MEM:

		if (ctxt->lock_prefix)

			rc = segmented_cmpxchg(ctxt,

					       ctxt->dst.addr.mem,

					       &ctxt->dst.orig_val,

					       &ctxt->dst.val,

					       ctxt->dst.bytes);

					       op->addr.mem,

					       &op->orig_val,

					       &op->val,

					       op->bytes);

		else

			rc = segmented_write(ctxt,

					     ctxt->dst.addr.mem,

					     &ctxt->dst.val,

					     ctxt->dst.bytes);

					     op->addr.mem,

					     &op->val,

					     op->bytes);

		if (rc != X86EMUL_CONTINUE)

			return rc;

		break;

	case OP_MEM_STR:

		rc = segmented_write(ctxt,

				ctxt->dst.addr.mem,

				ctxt->dst.data,

				ctxt->dst.bytes * ctxt->dst.count);

				op->addr.mem,

				op->data,

				op->bytes * op->count);

		if (rc != X86EMUL_CONTINUE)

			return rc;

		break;

	case OP_XMM:

		write_sse_reg(ctxt, &ctxt->dst.vec_val, ctxt->dst.addr.xmm);

		write_sse_reg(ctxt, &op->vec_val, op->addr.xmm);

		break;

	case OP_MM:

		write_mmx_reg(ctxt, &ctxt->dst.mm_val, ctxt->dst.addr.mm);

		write_mmx_reg(ctxt, &op->mm_val, op->addr.mm);

		break;

	case OP_NONE:

		/* no writeback */
@@ -4769,9 +4767,17 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt) 
		goto done;



writeback:

	rc = writeback(ctxt);

	if (!(ctxt->d & NoWrite)) {

		rc = writeback(ctxt, &ctxt->dst);

		if (rc != X86EMUL_CONTINUE)

			goto done;

	}

	if (ctxt->d & SrcWrite) {

		BUG_ON(ctxt->src.type == OP_MEM || ctxt->src.type == OP_MEM_STR);

		rc = writeback(ctxt, &ctxt->src);

		if (rc != X86EMUL_CONTINUE)

			goto done;

	}



	/*

	 * restore dst type in case the decoding will be reused