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Subject: Re: [PATCH v10 11/11] vfio: Document nested stage control
To:     Zenghui Yu <yuzenghui@huawei.com>, eric.auger.pro@gmail.com,
        iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
        kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu, joro@8bytes.org,
        alex.williamson@redhat.com, jacob.jun.pan@linux.intel.com,
        yi.l.liu@intel.com, robin.murphy@arm.com
References: <20200320161911.27494-1-eric.auger@redhat.com>
 <20200320161911.27494-12-eric.auger@redhat.com>
 <26a85a63-6cc1-0348-e703-cb31ddd75339@huawei.com>
From:   Auger Eric <eric.auger@redhat.com>
Message-ID: <4df9f189-7a1b-be1f-0b1a-1669534a98d7@redhat.com>
Date:   Tue, 6 Oct 2020 17:29:22 +0200
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Hi Zenghui,

On 9/24/20 3:42 PM, Zenghui Yu wrote:
> Hi Eric,
> 
> On 2020/3/21 0:19, Eric Auger wrote:
>> The VFIO API was enhanced to support nested stage control: a bunch of
>> new iotcls, one DMA FAULT region and an associated specific IRQ.
>>
>> Let's document the process to follow to set up nested mode.
>>
>> Signed-off-by: Eric Auger <eric.auger@redhat.com>
> 
> [...]
> 
>> +The userspace must be prepared to receive faults. The VFIO-PCI device
>> +exposes one dedicated DMA FAULT region: it contains a ring buffer and
>> +its header that allows to manage the head/tail indices. The region is
>> +identified by the following index/subindex:
>> +- VFIO_REGION_TYPE_NESTED/VFIO_REGION_SUBTYPE_NESTED_DMA_FAULT
>> +
>> +The DMA FAULT region exposes a VFIO_REGION_INFO_CAP_PRODUCER_FAULT
>> +region capability that allows the userspace to retrieve the ABI version
>> +of the fault records filled by the host.
> 
> Nit: I don't see this capability in the code.

Thank you very much for the review. I am late doing the respin but I
will take into account all your comments.

Thanks!

Eric
> 
> 
> Thanks,
> Zenghui
>