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Re: [PATCH v3 11/13] x86/xen: use lazy_mmu_state when context-switching
- To: David Woodhouse <dwmw2@xxxxxxxxxxxxx>, David Hildenbrand <david@xxxxxxxxxx>, linux-mm@xxxxxxxxx
- From: Kevin Brodsky <kevin.brodsky@xxxxxxx>
- Date: Fri, 24 Oct 2025 17:05:07 +0200
- Cc: linux-kernel@xxxxxxxxxxxxxxx, Alexander Gordeev <agordeev@xxxxxxxxxxxxx>, Andreas Larsson <andreas@xxxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>, Borislav Petkov <bp@xxxxxxxxx>, Catalin Marinas <catalin.marinas@xxxxxxx>, Christophe Leroy <christophe.leroy@xxxxxxxxxx>, Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>, "David S. Miller" <davem@xxxxxxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Jann Horn <jannh@xxxxxxxxxx>, Juergen Gross <jgross@xxxxxxxx>, "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>, Lorenzo Stoakes <lorenzo.stoakes@xxxxxxxxxx>, Madhavan Srinivasan <maddy@xxxxxxxxxxxxx>, Michael Ellerman <mpe@xxxxxxxxxxxxxx>, Michal Hocko <mhocko@xxxxxxxx>, Mike Rapoport <rppt@xxxxxxxxxx>, Nicholas Piggin <npiggin@xxxxxxxxx>, Peter Zijlstra <peterz@xxxxxxxxxxxxx>, Ryan Roberts <ryan.roberts@xxxxxxx>, Suren Baghdasaryan <surenb@xxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, Vlastimil Babka <vbabka@xxxxxxx>, Will Deacon <will@xxxxxxxxxx>, Yeoreum Yun <yeoreum.yun@xxxxxxx>, linux-arm-kernel@xxxxxxxxxxxxxxxxxxx, linuxppc-dev@xxxxxxxxxxxxxxxx, sparclinux@xxxxxxxxxxxxxxx, xen-devel@xxxxxxxxxxxxxxxxxxxx, x86@xxxxxxxxxx
- Delivery-date: Fri, 24 Oct 2025 15:05:29 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
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@xxxxxxx>
>>> ---
>>
>> 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
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