Thread (58 messages) 58 messages, 8 authors, 2025-10-28

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

From: Demi Marie Obenour <hidden>
Date: 2025-10-24 22:53:01
Also in: linux-arm-kernel, linux-mm, lkml, sparclinux, xen-devel

On 10/24/25 10:51, David Hildenbrand wrote:
On 24.10.25 16:47, David Woodhouse wrote:
quoted
On Thu, 2025-10-23 at 22:06 +0200, David Hildenbrand wrote:
quoted
On 15.10.25 10:27, Kevin Brodsky wrote:
quoted
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 <redacted>
---

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)

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