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Re: [PATCH] xen: Put wait.c behind CONFIG_WAIT
- To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Thu, 12 Feb 2026 08:38:18 +0100
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- Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>, Anthony PERARD <anthony.perard@xxxxxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, Jason Andryuk <jason.andryuk@xxxxxxx>
- Delivery-date: Thu, 12 Feb 2026 07:38:32 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 11.02.2026 18:30, Andrew Cooper wrote:
> On 11/02/2026 5:01 pm, Jason Andryuk wrote:
>> wait.c is only used by vm_event.c. Make CONFIG_VM_EVENT select
>> CONFIG_WAIT, and use CONFIG_WAIT to control building it.
>>
>> Provide stubs of functions called from common code. entry.S needs an
>> ifdef to hide the symbol from the assembly.
>>
>> Also conditionalize .waitqueue_vcpu in struct vcpu to save space.
>>
>> Signed-off-by: Jason Andryuk <jason.andryuk@xxxxxxx>
>
> I'd really rather see the API/ABI changes required to purge wait.c
> entirely, but I guess this will do in the short term.
>
> Two things want further thought.
>
> First, because ARM uses per-vCPU stacks not per-pCPU stacks, it doesn't
> need this infrastructure in the first place, but it looks like it's
> still compiled in and half wired up. I suppose you don't notice because
> you compile out VM_EVENT on ARM too?
But if we want it compiled out altogether on Arm, ...
> Second CONFIG_WAIT isn't great name because there are many things it
> could be. I'd be tempted to just reuse CONFIG_VM_EVENT and go without
> CONFIG_WAIT. I do not want to see any new users of wait.c, and it will
> disappear at some point.
... don't we need a separate kconfig control, for it to be selected only
on x86 (or for it to be dependent on x86, and then imply-ed)? Imo
CONFIG_WAITQUEUE would be okay, as long as it won't have a prompt. We'd
then simply want to prevent further select-s / imply-s to appear.
Jan
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