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Subject: Re: [PATCH v10 11/11] vfio: Document nested stage control
To:     Eric Auger <eric.auger@redhat.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>
From:   Zenghui Yu <yuzenghui@huawei.com>
Message-ID: <26a85a63-6cc1-0348-e703-cb31ddd75339@huawei.com>
Date:   Thu, 24 Sep 2020 21:42:10 +0800
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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.


Thanks,
Zenghui