Re: [PATCH v3 08/13] iommu/arm-smmu-v3: Propate ssid_bits

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Hi Jean,

On 12/18/19 5:08 PM, Jean-Philippe Brucker wrote:
> On Tue, Dec 17, 2019 at 06:07:26PM +0100, Auger Eric wrote:
>> Hi Jean,
>>
>> On 12/9/19 7:05 PM, Jean-Philippe Brucker wrote:
>>
>> s/Propate/Propagate in the commit title.
>>> Now that we support substream IDs, initialize s1cdmax with the number of
>>> SSID bits supported by a master and the SMMU.
>>>
>>> Context descriptor tables are allocated once for the first master
>>> attached to a domain. Therefore attaching multiple devices with
>>> different SSID sizes is tricky, and we currently don't support it.
>>>
>>> As a future improvement it would be nice to at least support attaching a
>>> SSID-capable device to a domain that isn't using SSID, by reallocating
>>> the SSID table.
>> Isn't that use case relevant (I mean using both devices in a non SSID
>> use case). For platform devices you can work this around with FW but for
>> PCI devices?
> 
> Normally each device gets its own domain. Especially since PASID is a PCI
> Express capability, I expect them to be properly isolated with ACS, each
> with its own IOMMU group. So I don't think this is too relevant for the
> moment, it would be a quirk for a broken system.

OK

Eric
> 
> Thanks,
> Jean
> 




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