Re: [PATCH v3 1/5] iommu: Lock group->mutex in iommu_deferred_attach

Jason Gunthorpe
2025-08-18T14:17:57Z

On Fri, Aug 15, 2025 at 08:24:57AM +0000, Tian, Kevin wrote:
> > From: Nicolin Chen <nicolinc@nvidia.com>
> > Sent: Tuesday, August 12, 2025 6:59 AM
> >
> > The iommu_deferred_attach() is a runtime asynchronous function called by
> > iommu-dma function, which could race against other attach functions if it
> > accesses something in the dev->iommu_group.
>
> Is there a real racing scenario being observed or more theoretical?

I think the commit message should explain the actual reason this is
being done, which AFAICT because the new lockdeps added in following
patches will fail on this path otherwise.

Jason