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Subject: Re: [RFC PATCH v3 8/8] vfio: Add nested IOPF support
To:     Shenming Lu <lushenming@huawei.com>,
        Alex Williamson <alex.williamson@redhat.com>
References: <20210409034420.1799-1-lushenming@huawei.com>
 <20210409034420.1799-9-lushenming@huawei.com>
 <20210518125808.345b812c.alex.williamson@redhat.com>
 <ea8c92a8-6e51-8be6-de19-d5e6f1d5527f@huawei.com>
 <83747758-ceb6-b498-8d95-609fdd0d763b@huawei.com>
 <20210524161129.085503ad@x1.home.shazbot.org>
 <90b00e7d-7934-ee79-7643-e2949e2d3af4@huawei.com>
From:   Lu Baolu <baolu.lu@linux.intel.com>
Message-ID: <9daf8877-a538-2d19-f548-b00ea6f127df@linux.intel.com>
Date:   Thu, 27 May 2021 19:18:44 +0800
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Hi Shenming and Alex,

On 5/27/21 7:03 PM, Shenming Lu wrote:
>> I haven't fully read all the references, but who imposes the fact that
>> there's only one fault handler per device?  If type1 could register one
>> handler and the vfio-pci bus driver another for the other level, would
>> we need this path through vfio-core?
> If we could register more than one handler per device, things would become
> much more simple, and the path through vfio-core would not be needed.
> 
> Hi Baolu,
> Is there any restriction for having more than one handler per device?
> 

Currently, each device could only have one fault handler. But one device
might consume multiple page tables. From this point of view, it's more
reasonable to have one handler per page table.

Best regards,
baolu