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From: Julien Grall <julien@xen.org>
To: Stefano Stabellini <sstabellini@kernel.org>,
	Rahul Singh <Rahul.Singh@arm.com>
Cc: xen-devel <xen-devel@lists.xenproject.org>,
	Bertrand Marquis <Bertrand.Marquis@arm.com>,
	"Volodymyr_Babchuk@epam.com" <Volodymyr_Babchuk@epam.com>,
	"brian.woods@xilinx.com" <brian.woods@xilinx.com>
Subject: Re: [PATCH v3 0/3] Generic SMMU Bindings
Date: Tue, 2 Feb 2021 17:50:29 +0000	[thread overview]
Message-ID: <7ddc6e1b-41ce-37ae-f86e-39893f53a0ec@xen.org> (raw)
In-Reply-To: <alpine.DEB.2.21.2102020937480.29047@sstabellini-ThinkPad-T480s>

Hi,

On 02/02/2021 17:44, Stefano Stabellini wrote:
> On Tue, 2 Feb 2021, Rahul Singh wrote:
>> Hello Stefano,
>>
>>> On 26 Jan 2021, at 10:58 pm, Stefano Stabellini <sstabellini@kernel.org> 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.

SMMU support on Juno is not that interesting because IIRC the stream-ID 
is the same for all the devices. So it is all or nothing passthrough.

For other HW, this may be a useful feature. Yet we would need a way to 
group the devices for passthrough.

In this context, I would consider it more a feature than a bug because 
the SMMU driver never remotely work on such HW.

Cheers,

-- 
Julien Grall


  reply	other threads:[~2021-02-02 17:50 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-26 22:58 [PATCH v3 0/3] Generic SMMU Bindings Stefano Stabellini
2021-01-26 22:58 ` [PATCH v3 1/3] arm,smmu: switch to using iommu_fwspec functions Stefano Stabellini
2021-02-02 16:07   ` Rahul Singh
2021-01-26 22:58 ` [PATCH v3 2/3] arm,smmu: restructure code in preparation to new bindings support Stefano Stabellini
2021-02-02 16:09   ` Rahul Singh
2021-01-26 22:58 ` [PATCH v3 3/3] arm,smmu: add support for generic DT bindings. Implement add_device and dt_xlate Stefano Stabellini
2021-02-02 16:09   ` Rahul Singh
2021-02-02 16:07 ` [PATCH v3 0/3] Generic SMMU Bindings Rahul Singh
2021-02-02 17:44   ` Stefano Stabellini
2021-02-02 17:50     ` Julien Grall [this message]
2021-02-02 18:27       ` Stefano Stabellini
2021-02-02 18:43         ` Julien Grall
2021-02-03 17:14     ` Rahul Singh
2021-04-05 15:23 ` Julien Grall
2021-04-06 23:59   ` Stefano Stabellini
2021-04-07 15:43     ` Rahul Singh
2021-04-10  0:27     ` Stefano Stabellini
2021-04-12 10:20       ` Rahul Singh
2021-04-13  0:27         ` Stefano Stabellini
2021-04-14 10:42           ` Rahul Singh

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