On Sat, Feb 09, 2013 at 11:31:44AM +0200, Avi Kivity wrote:
> Some instructions write back the source operand, not just the destination.
> Add support for doing this via the decode flags.
>
We cannot really write back to memory operands. I feel it's deceiving to make
the code look like we can.
> Signed-off-by: Avi Kivity <avi.kivity@xxxxxxxxx>
> ---
> arch/x86/kvm/emulate.c | 47 ++++++++++++++++++++++++++---------------------
> 1 file changed, 26 insertions(+), 21 deletions(-)
>
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index 2b11318..18c86b5 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -152,6 +152,7 @@
> #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
> @@ -1708,45 +1709,42 @@ 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 */
> @@ -4717,9 +4715,16 @@ special_insn:
> goto done;
>
> writeback:
> - rc = writeback(ctxt);
> - if (rc != X86EMUL_CONTINUE)
> - goto done;
> + if (!(ctxt->d & NoWrite)) {
> + rc = writeback(ctxt, &ctxt->dst);
> + if (rc != X86EMUL_CONTINUE)
> + goto done;
> + }
> + if (ctxt->d & SrcWrite) {
> + rc = writeback(ctxt, &ctxt->src);
> + if (rc != X86EMUL_CONTINUE)
> + goto done;
> + }
>
> /*
> * restore dst type in case the decoding will be reused
> --
> 1.8.1.2
--
Gleb.
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