Paolo Bonzini <[email protected]> writes:
> Even on a store the optimization saves about 50 clock cycles,
> mostly because the jump in write_memory_operand becomes much more
> predictable.
>
> Reviewed-by: Paolo Bonzini <[email protected]>
> Signed-off-by: Paolo Bonzini <[email protected]>
Isn't the reviewed-by automatically implied ? :)
> ---
> arch/x86/kvm/emulate.c | 14 +++++++++-----
> 1 file changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
> index 594cb560947c..eaf0853ffaf9 100644
> --- a/arch/x86/kvm/emulate.c
> +++ b/arch/x86/kvm/emulate.c
> @@ -1589,7 +1589,7 @@ static int load_segment_descriptor(struct
> x86_emulate_ctxt *ctxt,
>
> static int prepare_memory_operand(struct x86_emulate_ctxt *ctxt,
> struct operand *op,
> - bool write)
> + bool read, bool write)
> {
> int rc;
> unsigned long gva;
> @@ -1605,6 +1605,10 @@ static int prepare_memory_operand(struct
> x86_emulate_ctxt *ctxt,
> if (rc != X86EMUL_CONTINUE)
> return rc;
>
> + /* optimisation - avoid slow emulated read if Mov */
> + if (!read)
> + return X86EMUL_CONTINUE;
> +
> if (likely(!kvm_is_error_hva(op->hva))) {
> rc = read_from_user(ctxt, op->hva, &op->val, size);
> if (!write)
> @@ -4699,14 +4703,14 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
> }
>
> if ((ctxt->src.type == OP_MEM) && !(ctxt->d & NoAccess)) {
> - rc = prepare_memory_operand(ctxt, &ctxt->src, false);
> + rc = prepare_memory_operand(ctxt, &ctxt->src, true, false);
> if (rc != X86EMUL_CONTINUE)
> goto done;
> ctxt->src.orig_val64 = ctxt->src.val64;
> }
>
> if (ctxt->src2.type == OP_MEM) {
> - rc = prepare_memory_operand(ctxt, &ctxt->src2, false);
> + rc = prepare_memory_operand(ctxt, &ctxt->src2, true, false);
> if (rc != X86EMUL_CONTINUE)
> goto done;
> }
> @@ -4715,9 +4719,9 @@ int x86_emulate_insn(struct x86_emulate_ctxt *ctxt)
> goto special_insn;
>
>
> - if ((ctxt->dst.type == OP_MEM) && !(ctxt->d & Mov)) {
> - /* optimisation - avoid slow emulated read if Mov */
> + if (ctxt->dst.type == OP_MEM) {
> rc = prepare_memory_operand(ctxt, &ctxt->dst,
> + !(ctxt->d & Mov),
> !(ctxt->d & NoWrite));
> if (rc != X86EMUL_CONTINUE)
> goto done;
--
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