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Date: Mon, 23 Mar 2026 15:51:40 -0700
From: Jacob Pan <jacob.pan@linux.microsoft.com>
To: Mostafa Saleh <smostafa@google.com>
Cc: linux-kernel@vger.kernel.org, "iommu@lists.linux.dev"
 <iommu@lists.linux.dev>, Jason Gunthorpe <jgg@nvidia.com>, Alex Williamson
 <alex@shazbot.org>, Joerg Roedel <joro@8bytes.org>, David Matlack
 <dmatlack@google.com>, Robin Murphy <robin.murphy@arm.com>, Nicolin Chen
 <nicolinc@nvidia.com>, "Tian, Kevin" <kevin.tian@intel.com>, Yi Liu
 <yi.l.liu@intel.com>, skhawaja@google.com, pasha.tatashin@soleen.com, Will
 Deacon <will@kernel.org>, Baolu Lu <baolu.lu@linux.intel.com>
Subject: Re: [PATCH V2 02/11] iommufd: Move igroup allocation to a function
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Hi Mostafa,

On Sun, 22 Mar 2026 09:41:17 +0000
Mostafa Saleh <smostafa@google.com> wrote:

> On Thu, Mar 12, 2026 at 08:56:28AM -0700, Jacob Pan wrote:
> > From: Jason Gunthorpe <jgg@nvidia.com>
> > 
> > So it can be reused in the next patch which allows binding to
> > noiommu device.
> > 
> > Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
> > Signed-off-by: Jacob Pan <jacob.pan@linux.microsoft.com>
> > ---
> >  drivers/iommu/iommufd/device.c | 48
> > +++++++++++++++++++++------------- 1 file changed, 30
> > insertions(+), 18 deletions(-)
> > 
> > diff --git a/drivers/iommu/iommufd/device.c
> > b/drivers/iommu/iommufd/device.c index 344d620cdecc..54d73016468f
> > 100644 --- a/drivers/iommu/iommufd/device.c
> > +++ b/drivers/iommu/iommufd/device.c
> > @@ -30,8 +30,9 @@ static void iommufd_group_release(struct kref
> > *kref) 
> >  	WARN_ON(!xa_empty(&igroup->pasid_attach));
> >  
> > -	xa_cmpxchg(&igroup->ictx->groups,
> > iommu_group_id(igroup->group), igroup,
> > -		   NULL, GFP_KERNEL);
> > +	if (igroup->group)
> > +		xa_cmpxchg(&igroup->ictx->groups,
> > iommu_group_id(igroup->group),
> > +			   igroup, NULL, GFP_KERNEL);  
> 
> Is that a separate fix or perhaps belongs to the next patch making
> it possible to have NULL groups.
Yes, I agree. NULL groups are not possible here. Should be merged with
the next patch.