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

Kevin Brodsky
2025-10-24T15:05:18Z

On 24/10/2025 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?

I considered boot-testing a Xen guest (considering the Xen-specific
changes in this series), but having no idea how to go about it I quickly
gave up... Happy to follow instructions :)

- Kevin