Re: [Xen-devel] [PATCH RFC 1/9] xen: Emulate with no writes; compute current instruction length

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 02.07.14 at 17:43, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
> On 07/02/2014 06:21 PM, Jan Beulich wrote:
>>> +    struct x86_emulate_ctxt __attribute__((unused)) *ctxt)
>> 
>> We don't mark unused function arguments like this (and if we did,
>> we'd want you to use __maybe_unused).
> 
> OK, thanks. What's the proper way to mark them? Should I go with
> __maybe_unused then?

No - don't mark them.

>>> +void hvm_emulate_one_full(bool_t nowrite)
>>> +{
>>> +    struct hvm_emulate_ctxt ctx[1] = {};
>>> +    int rc = X86EMUL_RETRY;
>>> +
>>> +    hvm_emulate_prepare(ctx, guest_cpu_user_regs());
>>> +
>>> +    while ( rc == X86EMUL_RETRY )
>>> +    {
>>> +        if ( nowrite )
>>> +            rc = hvm_emulate_one_no_write(ctx);
>>> +        else
>>> +            rc = hvm_emulate_one(ctx);
>>> +    }
>>> +
>>> +    switch ( rc )
>>> +    {
>>> +    case X86EMUL_UNHANDLEABLE:
>>> +        hvm_inject_hw_exception(TRAP_invalid_op, 
> HVM_DELIVER_NO_ERROR_CODE);
>> 
>> Is it certain that #UD is always the right exception here?
> 
> For our purposes, yes.

That's not really a good answer for code that isn't there to only suit
you.

> Of course, that means that I can't really explain what the original
> author intended (related to the rest of your critique).

Which clearly won't help acceptance of this code, assuming that's
your goal.

Jan


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