Re: IOMMU regression in linux-6.18.y

Mario Limonciello
2026-01-21T05:26:18Z

On 1/20/26 8:08 PM, Mario Limonciello wrote:
> Hi,
>
> Recently I found out that amdxdna stopped working in linux-6.18.4.  This
> is because of this commit in linux-6.18.y:
>
> commit c341dee80b5d ("iommu: disable SVA when CONFIG_X86 is set")
>
> That was originally backported from upstream:
>
> commit 72f98ef9a4be ("iommu: disable SVA when CONFIG_X86 is set")
>
> ---
>
> SVA support is a requirement for amdxdna.
>
> The series that this commit came from was part of a larger 8 patch
> series, but this was the only commit that was CC'ed to stable.
>
> As a result this is not broken in 6.19-rc, but it is broken in
> linux-6.18.y (and presumably any older stable kernels still around that
> picked it up).
>
> So there are two options I see:
>
> 1) Revert c341dee80b5d in linux-6.18.y (and any other stable kernel that
> picked it up but has amdxdna)
>
> 2) Bring the entire 8 patch series to linux-6.18.y.
>
> This is the entire series (I didn't look up the hashes from mainline,
> but they should have all landed):
> https://lore.kernel.org/linux-iommu/20251022082635.2462433-1-
> baolu.lu@linux.intel.com/
>
> What should we do?
>

If the decision is to take the remaining commits to 6.18.y to fix this I
did confirm they cleanly cherry pick and build. Here are the hashes.

commit 27bfafac65d8 ("mm: add a ptdesc flag to mark kernel page tables")
commit 977870522af3 ("mm: actually mark kernel page table pages")
commit 412d000346ea ("x86/mm: use 'ptdesc' when freeing PMD pages")
commit 018942956723 ("mm: introduce pure page table freeing function")
commit bf9e4e30f353 ("x86/mm: use pagetable_free()")
commit 5ba2f0a15564 ("mm: introduce deferred freeing for kernel page
tables")
commit e37d5a2d60a3 ("iommu/sva: invalidate stale IOTLB entries for
kernel address space")