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Message-ID: <1497854312.4207.4.camel@redhat.com>
Subject: Re: [PATCH v9 5/7] vfio: Define vfio based dma-buf operations
From: Gerd Hoffmann <kraxel@redhat.com>
To: Kirti Wankhede <kwankhede@nvidia.com>,
        Alex Williamson <alex.williamson@redhat.com>
Cc: Xiaoguang Chen <xiaoguang.chen@intel.com>, chris@chris-wilson.co.uk,
        intel-gfx@lists.freedesktop.org, linux-kernel@vger.kernel.org,
        zhenyuw@linux.intel.com, zhiyuan.lv@intel.com,
        intel-gvt-dev@lists.freedesktop.org, zhi.a.wang@intel.com,
        kevin.tian@intel.com
Date: Mon, 19 Jun 2017 08:38:32 +0200
In-Reply-To: <24c4880b-24f5-ea07-834c-c77d3e895c78@nvidia.com>
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         <1497513611-2814-6-git-send-email-xiaoguang.chen@intel.com>
         <f19da207-a7f5-d3d3-4577-b071e7d75cf7@nvidia.com>
         <1497542438.29252.1.camel@redhat.com> <20170615143833.7526351b@w520.home>
         <24c4880b-24f5-ea07-834c-c77d3e895c78@nvidia.com>
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  Hi,

> My suggestion was to use vfio device fd for this ioctl and have
> dmabuf
> mgr fd as member in above query_plane structure, for region type it
> would be set to 0.

Region type should be DRM_PLANE_TYPE_PRIMARY

> Can't mmap that page to get surface information. There is no way to
> synchronize between QEMU reading this mmapped region and vendor
> driver
> writing it. There could be race condition in these two operations.
> Read
> on this page should be trapped and blocking, so that surface in that
> region is only updated when its asked for.

Does it make sense to have a "generation" field in the plane_info
struct (which gets increased each time the struct changes) ?

cheers,
  Gerd