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Subject: Re: [PATCH V4 05/18] iommu/ioasid: Redefine IOASID set and allocation
 APIs
To:     Jason Gunthorpe <jgg@nvidia.com>
Cc:     "Tian, Kevin" <kevin.tian@intel.com>,
        Alex Williamson <alex.williamson@redhat.com>,
        "Liu, Yi L" <yi.l.liu@intel.com>,
        Jacob Pan <jacob.jun.pan@linux.intel.com>,
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        LKML <linux-kernel@vger.kernel.org>,
        Joerg Roedel <joro@8bytes.org>,
        Lu Baolu <baolu.lu@linux.intel.com>,
        David Woodhouse <dwmw2@infradead.org>,
        "iommu@lists.linux-foundation.org" <iommu@lists.linux-foundation.org>,
        "cgroups@vger.kernel.org" <cgroups@vger.kernel.org>,
        Tejun Heo <tj@kernel.org>, Li Zefan <lizefan@huawei.com>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Jean-Philippe Brucker <jean-philippe@linaro.com>,
        Jonathan Corbet <corbet@lwn.net>,
        "Raj, Ashok" <ashok.raj@intel.com>, "Wu, Hao" <hao.wu@intel.com>,
        "Jiang, Dave" <dave.jiang@intel.com>
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 <20210429200431.GA1370958@nvidia.com>
From:   Auger Eric <eric.auger@redhat.com>
Message-ID: <17ab53a6-c2d7-c085-6469-ae487b138526@redhat.com>
Date:   Wed, 5 May 2021 11:10:29 +0200
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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
>