> > + if (insn_size) {
> > + run->emulation_failure.ndata = 3;
> > + run->emulation_failure.flags |=
> > + KVM_INTERNAL_ERROR_EMULATION_FLAG_INSTRUCTION_BYTES;
> > + run->emulation_failure.insn_size = insn_size;
> > + memcpy(run->emulation_failure.insn_bytes,
> > + ctxt->fetch.data, sizeof(ctxt->fetch.data));
>
> We're relying on the fact that insn_bytes is at least as large as
> fetch.data, which is fine, but worth an assertion?
>
> "Leaking" irrelevant bytes here also seems bad, but I can't immediately
> see a problem as a result.
>
I don't think this is a problem because the instruction bytes stream
has irrelevant bytes in it anyway. In the test attached I verify that
it receives an flds instruction in userspace that was emulated in the
guest. In the stream that comes through insn_size is set to 15 and
the instruction is only 2 bytes long, so the stream has irrelevant
bytes in it as far as this instruction is concerned.
> > + }
> > +}
> > +
