Re: [PATCH V4 05/18] iommu/ioasid: Redefine IOASID set and allocation APIs

Auger Eric
2021-05-05T09:10:29Z

Hi Jason,

On 4/29/21 10:04 PM, Jason Gunthorpe wrote:
> On Thu, Apr 29, 2021 at 03:26:55PM +0200, Auger Eric wrote:
>> From the pseudo code,
>>
>> gpa_ioasid_id = ioctl(ioasid_fd, CREATE_IOASID, ..)
>> ioctl(ioasid_fd, SET_IOASID_PAGE_TABLES, ..)
>>
>> I fail to understand whether the SET_IOASID_PAGE_TABLES would apply to
>> the whole IOASIDs within /dev/ioasid or to a specific one.
>
> Sorry, nearly every IOCTL would be scoped to a specific IOASID as one
> of the arguments.

OK thank you for the clarification.
>
>> Also in subsequent emails when you talk about IOASID, is it the
>> ioasid_id, just to double check the terminology.
>
> I am refering to IOASID as 'handle of the page table object inside the
> /dev/ioasid fd'. If that is equal to some HW value or not I think
> remains as decision point.
OK
>
> Basically the fd has an xarray of 'struct [something] *' and the
> IOASID is index to that FD's private xarray. This is necessary to
> create proper security as even if we have global PASID numbers or
> something they still need to be isolated to only the FD that has
> been authorized access.
>
>>> nested_ioasid = ioctl(ioasid_fd, CREATE_NESTED_IOASID, gpa_ioasid_id);
>>> ioctl(ioasid_fd, SET_NESTED_IOASID_PAGE_TABLES, nested_ioasid, ..)
>> is the nested_ioasid the allocated PASID id or is it a complete
>> different object id.
>
> It is the IOASID handle above.
ok as per the following emails and below comment IOASID and PASID are
different.The first would be a logic ID wgile the second the HW ID.

Thanks

Eric
>
>>>
>>> // IOMMU will match on the device RID, no PASID:
>>> ioctl(vfio_device, ATTACH_IOASID, nested_ioasid);
>>>
>>> // IOMMU will match on the device RID and PASID:
>>> ioctl(vfio_device, ATTACH_IOASID_PASID, pasid, nested_ioasid);
>> here I see you pass a different pasid, so I guess they are different, in
>> which case you would need to have an allocator function for this pasid,
>> right?
>
> Yes, the underlying HW ID (PASID or substream id or whatver) is
> something slightly different
>
> Jason
>