Re: [Qemu-trivial] [Qemu-devel] [PATCH] ide: log error when trying to use ATAPI overlapping features

[Stefan Hajnoczi]

On Mon, Feb 11, 2013 at 3:34 PM, Peter Maydell <address@hidden> wrote:
> On 11 February 2013 14:19, Andreas Färber <address@hidden> wrote:
>> Am 11.02.2013 15:01, schrieb Markus Armbruster:
>>> Kevin Wolf <address@hidden> writes:
>>>
>>>> Am 11.02.2013 14:27, schrieb Stefan Hajnoczi:
>>>>> I think we need to side-track this patch email to figure out what to
>>>>> use:
>>>>>
>>>>> fprintf(stderr) - some warnings/errors use this
>>>>> error_report() - goes to the monitor, if possible, otherwise stderr
>>>>
>>>> These look wrong to me.
>>>
>>> "Wrong" is a bit strong, in particular since there's ample precedence
>>> for these uses.
>
> Certainly for fprintf() I would say "deprecated" wherever
> we have a better API available.
>
>>>>> qemu_log_*() - goes to the qemu log, seems a little TCG-centric
>>>>
>>>> I would suggest either this or just trace points. (And by the way, it's
>>>> a pity that -d is so TCG-centric, it's been more than once the reason
>>>> why I disabled KVM when debugging a guest... Having at least -d int
>>>> would be so useful.)
>>>
>>> Tracepoints don't really fit when we want to report the guest does
>>> something we don't handle.  Users deserve fair warning then, don't they?
>>>
>>> Could qemu_log() & friends be made fit for general use?  What's missing?
>>
>> Blue already did some work to make it more usable, and I believe Peter
>> adopted LOG_UNIMPL for ARM devices in place of hw_error()
>
> Yes; in particular where we have classes of error message which the
> user may wish to enable or disable (of which "QEMU doesn't implement
> this" and "the guest just did something that's probably a guest bug"
> are two common ones) qemu_log_mask(LOG_*, ...) is the preferred
> API for devices IMHO. So I think Herve's patch is entirely the
> right thing.

qemu_log_mask() can replace fprintf() but it needs to default to
stderr and a reasonable default mask.  It should be used for
non-monitor command errors and warnings.

Having said that, I think we should use hw_error() or fprintf() in
this patch until qemu_log_mask() replaces them.

Stefan