Re: [PATCH v5 07/12] mm: bail out of lazy_mmu_mode_* in interrupt context

["David Hildenbrand (Red Hat)" <david@xxxxxxxxxx>]

On 11/24/25 14:22, Kevin Brodsky wrote:
> The lazy MMU mode cannot be used in interrupt context. This is
> documented in <linux/pgtable.h>, but isn't consistently handled
> across architectures.
>
> arm64 ensures that calls to lazy_mmu_mode_* have no effect in
> interrupt context, because such calls do occur in certain
> configurations - see commit b81c688426a9 ("arm64/mm: Disable barrier
> batching in interrupt contexts"). Other architectures do not check
> this situation, most likely because it hasn't occurred so far.
>
> Let's handle this in the new generic lazy_mmu layer, in the same
> fashion as arm64: bail out of lazy_mmu_mode_* if in_interrupt().
> Also remove the arm64 handling that is now redundant.
>
> Both arm64 and x86/Xen also ensure that any lazy MMU optimisation is
> disabled while in interrupt (see queue_pte_barriers() and
> xen_get_lazy_mode() respectively). This will be handled in the
> generic layer in a subsequent patch.
>
> Signed-off-by: Kevin Brodsky <kevin.brodsky@xxxxxxx>
> ---
(resending as I pushed the wrong button there ...)

Moving this patch earlier LGTM, hoping we don't get any unexpected
surprises ...

Acked-by: David Hildenbrand (Red Hat) <david@xxxxxxxxxx>

--
Cheers

David