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

  • To: Stefano Stabellini <sstabellini@xxxxxxxxxx>
  • From: Rahul Singh <Rahul.Singh@xxxxxxx>
  • Date: Wed, 3 Feb 2021 17:14:45 +0000
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  • Thread-topic: [PATCH v3 0/3] Generic SMMU Bindings

Hello Stefano,

> On 2 Feb 2021, at 5:44 pm, Stefano Stabellini <sstabellini@xxxxxxxxxx> wrote:
> 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?

Yes I am happy to backport these patches to XEN. 
I will send the patch for review once 4.15 release branch out from master.
> 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.



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