Re: [PATCH v2 01/20] memory: Adjust event ranges to fit within notifier boundaries

[Peter Xu <peterx@redhat.com>]

On Mon, May 12, 2025 at 10:02:16AM +0200, David Hildenbrand wrote:
> On 02.05.25 04:15, Alejandro Jimenez wrote:
> > Invalidating the entire address space (i.e. range of [0, ~0ULL]) is a
> > valid and required operation by vIOMMU implementations. However, such
> > invalidations currently trigger an assertion unless they originate from
> > device IOTLB invalidations.
> > 
> > Although in recent Linux guests this case is not exercised by the VTD
> > implementation due to various optimizations, the assertion will be hit
> > by upcoming AMD vIOMMU changes to support DMA address translation. More
> > specifically, when running a Linux guest with VFIO passthrough device,
> > and a kernel that does not contain commmit 3f2571fed2fa ("iommu/amd:
> > Remove redundant domain flush from attach_device()").
> > 
> > Remove the assertion altogether and adjust the range to ensure it does
> > not cross notifier boundaries.
> 
> Looking at the history, we used to have the assert unconditionally, and
> made it specific to IOMMU_NOTIFIER_DEVIOTLB_UNMAP in
> 
> commit 1804857f19f612f6907832e35599cdb51d4ec764
> Author: Eugenio Pérez <eperezma@redhat.com>
> Date:   Mon Nov 16 17:55:06 2020 +0100
> 
>     memory: Skip bad range assertion if notifier is DEVIOTLB_UNMAP type
>     Device IOTLB invalidations can unmap arbitrary ranges, eiter outside of
>     the memory region or even [0, ~0ULL] for all the space. The assertion
>     could be hit by a guest, and rhel7 guest effectively hit it.
>     Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
>     Reviewed-by: Peter Xu <peterx@redhat.com>
>     Reviewed-by: Juan Quintela <quintela@redhat.com>
>     Acked-by: Jason Wang <jasowang@redhat.com>
>     Message-Id: <20201116165506.31315-6-eperezma@redhat.com>
>     Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
>     Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> 
> 
> I think this change here is fine, but it would be good getting Pete Xu's opinion.

Agree, that could be an old sanity check only when it used to be guranteed.

> 
> Acked-by: David Hildenbrand <david@redhat.com>

Acked-by: Peter Xu <peterx@redhat.com>

-- 
Peter Xu