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Re: [PATCH 0/3] Change XEN_DOMCTL_setvcpuaffinity interface
- To: Jürgen Groß <jgross@xxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Thu, 2 Jul 2026 08:25:49 +0200
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- Cc: Anthony PERARD <anthony.perard@xxxxxxxxxx>, Dario Faggioli <dfaggioli@xxxxxxxx>, George Dunlap <gwd@xxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Julien Grall <julien@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Thu, 02 Jul 2026 06:26:00 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 02.07.2026 08:13, Jürgen Groß wrote:
> On 02.07.26 07:54, Jan Beulich wrote:
>> On 01.07.2026 17:34, Juergen Gross wrote:
>>> On 01.07.26 13:39, Jan Beulich wrote:
>>>> On 01.07.2026 13:16, Juergen Gross wrote:
>>>>> Today the XEN_DOMCTL_setvcpuaffinity hypercall will not only change the
>>>>> affinity settings of a vcpu, it will return the new effective settings,
>>>>> too.
>>>>>
>>>>> In case an error happens during this hypercall, the expectation of the
>>>>> caller is that the affinity of the vcpu didn't change. This isn't true,
>>>>> however, if passing the new effective affinity back to the user is
>>>>> failing.
>>>>
>>>> That'll be the caller's fault though. Any -EFAULT coming back are an
>>>> indication that the caller needs fixing.
>>>
>>> The possible -ENOMEM isn't the callers fault, though.
>>
>> Yet that'll happen ahead of any changes made, won't it?
>
> No, it can happen during the final call of cpumask_to_xenctl_bitmap().
Only hypothetically, on a big-endian architecture (which we don't currently
have support for anywhere, hence why the little endian special case was
added there).
Jan
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