Re: IOMMU regression in linux-6.18.y

[Mario Limonciello <superm1@kernel.org>]

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")