linux-kernel - Re: [Patch V2 0/2] iommu/arm-smmu: Fix races in iommu domain/group creation

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Date:   Mon, 9 Aug 2021 15:54:20 +0100
From:   Will Deacon <will@...nel.org>
To:     Robin Murphy <robin.murphy@....com>
Cc:     Ashish Mhetre <amhetre@...dia.com>, vdumpa@...dia.com,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [Patch V2 0/2] iommu/arm-smmu: Fix races in iommu domain/group
 creation

On Mon, Aug 02, 2021 at 04:46:37PM +0100, Robin Murphy wrote:
> On 2021-08-02 16:16, Will Deacon wrote:
> > On Fri, Jun 18, 2021 at 02:00:35AM +0530, Ashish Mhetre wrote:
> > > Multiple iommu domains and iommu groups are getting created for the devices
> > > sharing same SID. It is expected for devices sharing same SID to be in same
> > > iommu group and same iommu domain.
> > > This is leading to context faults when one device is accessing IOVA from
> > > other device which shouldn't be the case for devices sharing same SID.
> > > Fix this by protecting iommu domain and iommu group creation with mutexes.
> > 
> > Robin -- any chance you could take a look at these, please? You had some
> > comments on the first version which convinced me that they are needed,
> > but I couldn't tell whether you wanted to solve this a different way or not.
> 
> Sorry, I was lamenting that this came to light due to the
> of_iommu_configure() flow being yucky, but that wasn't meant to imply that
> there aren't - or couldn't be in future - better reasons for
> iommu_probe_device() to be robust against concurrency anyway. I do think
> these are legitimate fixes to make in their own right, even if the current
> need might get swept back under the rug in future.
> 
> I would say, however, that the commit messages seem to focus too much on the
> wrong details and aren't overly useful, and patch #2 is missing Ashish's
> sign-off.

Ashish -- please can you send a v3 fixing these issues?

Will