Re: [PATCH v3 11/13] x86/xen: use lazy_mmu_state when context-switching

David Hildenbrand
2025-10-24T15:47:19Z

On 24.10.25 17:38, John Paul Adrian Glaubitz wrote:
> On Fri, 2025-10-24 at 16:13 +0100, David Woodhouse wrote:
>> On Fri, 2025-10-24 at 16:51 +0200, David Hildenbrand wrote:
>>> On 24.10.25 16:47, David Woodhouse wrote:
>>>> On Thu, 2025-10-23 at 22:06 +0200, David Hildenbrand wrote:
>>>>> On 15.10.25 10:27, Kevin Brodsky wrote:
>>>>>> We currently set a TIF flag when scheduling out a task that is in
>>>>>> lazy MMU mode, in order to restore it when the task is scheduled
>>>>>> again.
>>>>>>
>>>>>> The generic lazy_mmu layer now tracks whether a task is in lazy MMU
>>>>>> mode in task_struct::lazy_mmu_state. We can therefore check that
>>>>>> state when switching to the new task, instead of using a separate
>>>>>> TIF flag.
>>>>>>
>>>>>> Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
>>>>>> ---
>>>>>
>>>>>
>>>>> Looks ok to me, but I hope we get some confirmation from x86 / xen
>>>>> folks.
>>>>
>>>>
>>>> I know tglx has shouted at me in the past for precisely this reminder,
>>>> but you know you can test Xen guests under QEMU/KVM now and don't need
>>>> to actually run Xen? Has this been boot tested?
>>>
>>> And after that, boot-testing sparc as well? :D
>>
>> Also not that hard in QEMU, I believe. Although I do have some SPARC
>> boxes in the shed...
>
> Please have people test kernel changes on SPARC on real hardware. QEMU does not
> emulate sun4v, for example, and therefore testing in QEMU does not cover all
> of SPARC hardware.
>
> There are plenty of people on the debian-sparc, gentoo-sparc and sparclinux
> LKML mailing lists that can test kernel patches for SPARC. If SPARC-relevant
> changes need to be tested, please ask there and don't bury such things in a
> deeply nested thread in a discussion which doesn't even have SPARC in the
> mail subject.

Hi Adrian,

out of curiosity, do people monitor sparclinux@ for changes to actively
offer testing when required -- like would it be sufficient to CC
relevant maintainers+list (like done here) and raise in the cover letter
that some testing help would be appreciated?

--
Cheers

David / dhildenb