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Re: [PATCH v2] libxc: avoid clobbering errno in xc_domain_pod_target()
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Bertrand Marquis <Bertrand.Marquis@xxxxxxx>
- Date: Fri, 10 Dec 2021 14:00:06 +0000
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Anthony Perard <anthony.perard@xxxxxxxxxx>, Juergen Gross <jgross@xxxxxxxx>
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- Thread-topic: [PATCH v2] libxc: avoid clobbering errno in xc_domain_pod_target()
Hi Jan,
> On 10 Dec 2021, at 13:54, Jan Beulich <jbeulich@xxxxxxxx> wrote:
>
> On 10.12.2021 14:50, Bertrand Marquis wrote:
>>> On 10 Dec 2021, at 13:11, Jan Beulich <jbeulich@xxxxxxxx> wrote:
>>>
>>> do_memory_op() supplies return value and has "errno" set the usual way.
>>> Don't overwrite "errno" with 1 (aka EPERM on at least Linux). There's
>>> also no reason to overwrite "err".
>>>
>>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>> Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
>
> Thanks.
>
>> But if err can really only be 0 or -1, I do wonder if the else forcing err
>> to 0 could
>> be removed but I must say I have no idea if do_memory_op could return a
>> value >0.
>
> Indeed - see ...
>
>>> ---
>>> While the hypervisor side of the hypercall gives the impression of being
>>> able to return positive values as of 637a283f17eb ("PoD: Allow
>>> pod_set_cache_target hypercall to be preempted"), due to the use of
>>> "rc >= 0" there, afaict that's not actually the case. IOW "err" can
>>> really only be 0 or -1 here, and hence its setting to zero may also be
>>> worthwhile to drop.
>>> ---
>
> ... this.
So the else should be dropped then, why not doing it and just mentioning it
there ?
Bertrand
>
> Jan
>
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