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Re: [PATCH v3 11/13] x86/xen: use lazy_mmu_state when context-switching
- To: David Hildenbrand <david@xxxxxxxxxx>, David Woodhouse <dwmw2@xxxxxxxxxxxxx>, Kevin Brodsky <kevin.brodsky@xxxxxxx>, linux-mm@xxxxxxxxx
- From: Demi Marie Obenour <demiobenour@xxxxxxxxx>
- Date: Fri, 24 Oct 2025 18:52:50 -0400
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- 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 22:53:23 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 10/24/25 10:51, 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@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?
>
> And after that, boot-testing sparc as well? :D
>
> If it's easy, why not. But other people should not suffer for all the
> XEN hacks we keep dragging along.
Which hacks? Serious question. Is this just for Xen PV or is HVM
also affected?
--
Sincerely,
Demi Marie Obenour (she/her/hers) Attachment:
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