On Tue, May 22, 2012 at 2:38 PM, Kevin Wolf <kwolf@xxxxxxxxxx> wrote:
> Am 22.05.2012 15:25, schrieb Corey Bryant:
>>
>>
>> On 05/21/2012 05:40 PM, Eric Blake wrote:
>>> On 05/21/2012 02:19 PM, Corey Bryant wrote:
>>>> This patch provides support for the -filefd command line option.
>>>> This option will allow passing of a filename and its corresponding
>>>> file descriptor to QEMU at exec time.
>>>>
>>>> Signed-off-by: Corey Bryant<coreyb@xxxxxxxxxxxxxxxxxx>
>>>
>>>> +DEF("filefd", HAS_ARG, QEMU_OPTION_filefd,
>>>> + "-filefd file=<filename>,fd=<fd>\n"
>>>
>>> I take it that if filename contains ',', then we have to escape it on
>>> the command line? Is it worth passing fd first and file second by
>>> default, as a possible way to avoid the need for escaping, or does the
>>> option parser not care about ordering?
>>>
>>
>> That's a good question. The options can be ordered either way so I
>> don't think we'll force fd to be specified first. I imagine this should
>> behave no differently than "-drive file=xyz,if=none,...". I ran a quick
>> test using -drive with a filename that had a comma, and (escaped or not)
>> it failed on the option parsing. So it looks like if you have a path
>> with a comma you're not going to have any luck.
>
> I think you can escape it, you'd have to use a double comma. But I'd
> rather not introduce more of this. It's another good reason for using
> /dev/fd/... instead of a translation table.
I'm not sure how this solves backing file descriptor passing? How
will QEMU know to use /dev/fd/10 for a backing file that is referenced
from /dev/fd/9 as "backing.img"? (There was discussion about
rewriting backing filenames but I think that solution is risky and we
should avoid it.)
Stefan
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