Re: [PATCH v2 01/40] iommu: Introduce Shared Virtual Addressing API

Jean-Philippe Brucker
2018-09-06T12:45:36Z

On 06/09/2018 12:12, Christian König wrote:
> Am 06.09.2018 um 13:09 schrieb Jean-Philippe Brucker:
>> Hi Eric,
>>
>> Thanks for reviewing
>>
>> On 05/09/2018 12:29, Auger Eric wrote:
>>>> +int iommu_sva_device_init(struct device *dev, unsigned long features,
>>>> +              unsigned int max_pasid)
>>> what about min_pasid?
>> No one asked for it... The max_pasid parameter is here for drivers that
>> have vendor-specific PASID size limits, such as AMD KFD (see
>> kfd_iommu_device_init and
>> https://patchwork.kernel.org/patch/9989307/#21389571). But in most cases
>> the PASID size will only depend on the PCI PASID capability and the
>> IOMMU limits, both known by the IOMMU driver, so device drivers won't
>> have to set max_pasid.
>>
>> IOMMU drivers need to set min_pasid in the sva_device_init callback
>> because it may be either 1 (e.g. Arm where PASID #0 is reserved) or 0
>> (Intel Vt-d rev2), but at the moment I can't see a reason for device
>> drivers to override min_pasid
>
> Sorry to ruin your day, but if I'm not completely mistaken PASID zero is
> reserved in the AMD KFD as well.

Heh, fair enough. I'll add the min_pasid parameter

Thanks,
Jean
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