Re: [PATCH v3 0/3] Generic SMMU Bindings

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 2 Feb 2021, Rahul Singh wrote:
> Hello Stefano,
> 
> > On 26 Jan 2021, at 10:58 pm, Stefano Stabellini <sstabellini@xxxxxxxxxx> 
> > wrote:
> > 
> > Hi all,
> > 
> > This series introduces support for the generic SMMU bindings to
> > xen/drivers/passthrough/arm/smmu.c.
> > 
> > The last version of the series was
> > https://marc.info/?l=xen-devel&m=159539053406643
> > 
> > I realize that it is late for 4.15 -- I think it is OK if this series
> > goes in afterwards.
> 
> I tested the series on the Juno board it is woking fine.  
> I found one issue in SMMU driver while testing this series that is not 
> related to this series but already existing issue in SMMU driver.
> 
> If there are more than one device behind SMMU and they share the same 
> Stream-Id, SMMU driver is creating the new SMR entry without checking the 
> already configured SMR entry if SMR entry correspond to stream-id is already 
> configured.  Because of this I observed the stream match conflicts on Juno 
> board.
> 
> (XEN) smmu: /iommu@7fb30000: Unexpected global fault, this could be serious
> (XEN) smmu: /iommu@7fb30000:  GFSR 0x00000004, GFSYNR0 0x00000006, GFSYNR1 
> 0x00000000, GFSYNR2 0x00000000
> 
> 
> Below two patches is required to be ported to Xen to fix the issue from Linux 
> driver.
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/drivers/iommu/arm-smmu.c?h=linux-5.8.y&id=1f3d5ca43019bff1105838712d55be087d93c0da
> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/drivers/iommu/arm-smmu.c?h=linux-5.8.y&id=21174240e4f4439bb8ed6c116cdbdc03eba2126e


Good catch and thanks for the pointers! Do you have any interest in
backporting these two patches or should I put them on my TODO list?

Unrelated to who does the job, we should discuss if it makes sense to
try to fix the bug for 4.15. The patches don't seem trivial so I am
tempted to say that it might be best to leave the bug unfixed for 4.15
and fix it later.