Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf operations

From	Gerd Hoffmann <kraxel@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf operations
Date	2017-06-26 08:40 +0200
Message-ID	<tWvQJ-7gm-1@gated-at.bofh.it> (permalink)
References	(6 earlier) <tTYvT-7uN-1@gated-at.bofh.it> <tU6jM-3YD-19@gated-at.bofh.it> <tUn1f-6h1-3@gated-at.bofh.it> <tUp34-7yf-13@gated-at.bofh.it> <tVEMq-7yC-19@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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  Hi,

> > With the generation we can also do something different:  Pass in
> > plane_type and
> > generation, and have VFIO_DEVICE_GET_DMABUF_FD return an error in
> > case
> > the generation doesn't match.  In that case it doesn't make much
> > sense any
> > more to have a separate plane_info struct, which was added so we
> > don't have
> > to duplicate things in query-plane and get- dmabuf ioctl structs.
> 
> Comparing with the current patch, this would make user space a little
> bit harder to
> get the dmabuf by calling VFIO_DEVICE_GET_DMABUF ioctl. Is it
> efficient for
> user mode usage?

user space has to call QUERY-PLANE first, then looks if it has a dma-
buf for that, if not call GET-DMABUF.

Problem is the guest could have changed the plane between the QUERY-
PLANE and GET-DMABUF ioctls.

Current patches (v8 series) just returns plane-info on GET-DMABUF too,
so userspace can at least detect something changed.

It would be easier for userspace if GET-DMABUF throws an error in case
the plane changed since the last QUERY-PLANE ioctl.  The generation id
would be one way to handle it, but possibly it is easier if the kernel
driver just keeps track internally.  So GET-DMABUF would be defined to
return a dmabuf for the plane returned by the previous QUERY-PLANE
ioctl (on the same file handle), or return an error in case the plane
has changed meanwhile.

cheers,
  Gerd

Thread

RE: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf         operations "Zhang, Tina" <tina.zhang@intel.com> - 2017-06-20 10:50 +0200
  Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf  operations Gerd Hoffmann <kraxel@redhat.com> - 2017-06-20 13:00 +0200
    Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf  operations Alex Williamson <alex.williamson@redhat.com> - 2017-06-20 17:10 +0200
      Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf  operations Kirti Wankhede <kwankhede@nvidia.com> - 2017-06-20 19:10 +0200
      RE: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf  operations "Zhang, Tina" <tina.zhang@intel.com> - 2017-06-21 01:10 +0200
        Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf  operations Alex Williamson <alex.williamson@redhat.com> - 2017-06-21 01:30 +0200
          RE: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf  operations "Zhang, Tina" <tina.zhang@intel.com> - 2017-06-21 11:30 +0200
            Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf  operations Gerd Hoffmann <kraxel@redhat.com> - 2017-06-21 13:10 +0200
              Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf  operations Alex Williamson <alex.williamson@redhat.com> - 2017-06-21 21:00 +0200
                Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf  operations Gerd Hoffmann <kraxel@redhat.com> - 2017-06-22 10:40 +0200
                Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf  operations Alex Williamson <alex.williamson@redhat.com> - 2017-06-22 21:00 +0200
                Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf  operations Gerd Hoffmann <kraxel@redhat.com> - 2017-06-23 09:30 +0200
                Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf operations Zhi Wang <zhi.a.wang@intel.com> - 2017-06-23 10:10 +0200
                Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf  operations Gerd Hoffmann <kraxel@redhat.com> - 2017-06-23 10:40 +0200
                Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf  operations Alex Williamson <alex.williamson@redhat.com> - 2017-06-23 18:50 +0200
                Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf  operations Alex Williamson <alex.williamson@redhat.com> - 2017-06-23 19:20 +0200
                Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf  operations Gerd Hoffmann <kraxel@redhat.com> - 2017-06-26 08:20 +0200
              RE: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf  operations "Zhang, Tina" <tina.zhang@intel.com> - 2017-06-22 02:30 +0200
      Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf  operations Gerd Hoffmann <kraxel@redhat.com> - 2017-06-21 09:40 +0200
    RE: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf  operations "Zhang, Tina" <tina.zhang@intel.com> - 2017-06-24 00:00 +0200
      Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf  operations Gerd Hoffmann <kraxel@redhat.com> - 2017-06-26 08:40 +0200
        Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf  operations Alex Williamson <alex.williamson@redhat.com> - 2017-06-26 19:30 +0200
          Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf  operations Gerd Hoffmann <kraxel@redhat.com> - 2017-06-27 08:20 +0200
            RE: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf  operations "Zhang, Tina" <tina.zhang@intel.com> - 2017-06-28 14:50 +0200
              Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf  operations Gerd Hoffmann <kraxel@redhat.com> - 2017-06-29 08:50 +0200
                Re: [Intel-gfx] [PATCH v9 5/7] vfio: Define vfio based dma-buf  operations Daniel Vetter <daniel@ffwll.ch> - 2017-06-29 10:40 +0200

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