[Bug 220776] When passthrough device to KVM guest with iommufd+hugepage, more hugepage are used than assigned, and DMAR error reported from host dmesg

[bugzilla-daemon@kernel.org]

https://bugzilla.kernel.org/show_bug.cgi?id=220776

--- Comment #2 from Chen, Fan (farrah.chen@intel.com) ---
Involve the author steven.sistare@oracle.com of related patches to take 
a look.

Thanks,
Fan

On 11/11/2025 5:01 PM, bugzilla-daemon@kernel.org wrote:
> https://bugzilla.kernel.org/show_bug.cgi?id=220776
> 
> chenyi.qiang@intel.com changed:
> 
>             What    |Removed                     |Added
> ----------------------------------------------------------------------------
>                   CC|                            |chenyi.qiang@intel.com
> 
> --- Comment #1 from chenyi.qiang@intel.com ---
> After some bisect, it is found that this issue is introduced by the support
> of
> dma_map_file in iommufd [1][2]. With hugetlbfs as backend, it will go to the
> path of IOMMU_IOAS_MAP_FILE ioctl. If we fallback to the IOMMU_IOAS_MAP
> ioctl,
> there's no such problem.
> 
> [1]
>
> https://lore.kernel.org/qemu-devel/1751493538-202042-9-git-send-email-steven.sistare@oracle.com/
> [2]
>
> https://lore.kernel.org/all/1729861919-234514-1-git-send-email-steven.sistare@oracle.com/
>

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