Re: [PATCH] iommu/sva: Charge IOPF allocations to the faulting mm's memcg

[Baolu Lu]

On 10/13/2026 4:08 AM, Peizhe Liu wrote:
> iommu_sva_handle_mm() runs from the IOPF workqueue and calls
> handle_mm_fault() for the faulting mm, but does not set the active
> memcg. File-backed faults can allocate page cache through
> mem_cgroup_charge(folio, NULL, gfp), which falls back to the root memcg
> when the worker has neither an active memcg nor a current->mm. Page
> cache faulted in by a device is therefore charged to root and escapes
> the task's memory.max.
>
> Set the active memcg to the one associated with the faulting mm while
> handling the fault, and restore the previous value afterwards.
>
> Fixes: fc36479db74e ("iommu: Add a page fault handler")
> Signed-off-by: Peizhe Liu<peizheliu@xxxxxxxxxx>
> ---
> Tested on a Xeon Gold 5512U with Intel DSA, based on iommu/next.
> Before/after testing confirmed that the block-on-fault case charges
> the page cache to the task's memcg after this change and is subject
> to memory.max.
>
>   drivers/iommu/iommu-sva.c | 6 ++++++
>   1 file changed, 6 insertions(+)

Reviewed-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>