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From: Gerd Hoffmann <kraxel@redhat.com>
To: "Zhang, Tina" <tina.zhang@intel.com>,
	"zhenyuw@linux.intel.com" <zhenyuw@linux.intel.com>,
	"Wang, Zhi A" <zhi.a.wang@intel.com>,
	"Tian, Kevin" <kevin.tian@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>,
	"intel-gfx@lists.freedesktop.org"
	<intel-gfx@lists.freedesktop.org>,
	"intel-gvt-dev@lists.freedesktop.org"
	<intel-gvt-dev@lists.freedesktop.org>,
	"Lv, Zhiyuan" <zhiyuan.lv@intel.com>
Subject: Re: [PATCH v14 5/7] vfio: ABI for mdev display dma-buf operation
Date: Wed, 27 Sep 2017 12:11:04 +0200	[thread overview]
Message-ID: <1506507064.25036.5.camel@redhat.com> (raw)
In-Reply-To: <237F54289DF84E4997F34151298ABEBC7C5E5ADC@SHSMSX101.ccr.corp.intel.com>

  Hi,

> So, there is a problem about the releasing cached dmabuf_obj. We
> cannot rely on the drm_i915_gem_object_ops.release() to release the
> cached dmabuf_obj,
> as this release operation is running in another thread, which leads
> to a racing condition and tricky to be solved without touching other
> modules.

PLANE_INFO just creates a intel_vgpu_dmabuf_obj.

GET_DMABUF creates a fresh proxy gem object and dmabuf.

proxy gem object references intel_vgpu_dmabuf_obj but not the other way
around.  Then you can simply refcount intel_vgpu_dmabuf_obj and be done
with it.

https://www.kraxel.org/cgit/linux/commit/?h=gvt-dmabuf-v14&id=350a0e834
971e6f53d7235d8b6167bed4dccf074

Note: Patch renamed intel_vgpu_dmabuf_obj to intel_vgpu_fb_obj, because
it doesn't refer to dmabufs any more.  It basically carries the guest
plane/framebuffer information and the ID associated with it.

> So, in order to solve that kind of problem, I’d like to add one more
> ioctl, which is used for user mode to close the dmabuf_obj. 

Depending on userspace notifying the kernel for that kind of cleanups
is a bad idea.  What happens in case userspace crashes?  Do you leak
dmabufs then?

cheers,
  Gerd

_______________________________________________
Intel-gfx mailing list
Intel-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gfx

  reply	other threads:[~2017-09-27 10:11 UTC|newest]

Thread overview: 31+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-08-18 10:21 [PATCH v14 0/7] drm/i915/gvt: Dma-buf support for GVT-g Tina Zhang
2017-08-18 10:21 ` [PATCH v14 1/7] drm/i915/gvt: Add framebuffer decoder support Tina Zhang
2017-08-23  9:45   ` Zhenyu Wang
2017-08-18 10:21 ` [PATCH v14 2/7] drm: Introduce RGB 64-bit 16:16:16:16 float format Tina Zhang
2017-08-18 10:21 ` [PATCH v14 3/7] drm/i915/gvt: Add " Tina Zhang
2017-08-18 10:21 ` [PATCH v14 4/7] drm/i915/gvt: Add opregion support Tina Zhang
2017-08-18 10:21 ` [PATCH v14 5/7] vfio: ABI for mdev display dma-buf operation Tina Zhang
2017-08-22  8:33   ` Gerd Hoffmann
2017-09-26  7:12   ` Gerd Hoffmann
2017-09-27  9:03     ` Zhang, Tina
2017-09-27 10:11       ` Gerd Hoffmann [this message]
2017-09-28 23:43         ` Zhang, Tina
2017-09-29  7:11           ` Gerd Hoffmann
2017-09-29  7:04         ` Zhang, Tina
2017-09-29  7:28           ` Gerd Hoffmann
2017-09-29  7:49             ` Zhang, Tina
2017-09-29  8:03               ` Gerd Hoffmann
2017-09-29  9:08                 ` Zhang, Tina
2017-09-29 10:20                   ` Gerd Hoffmann
2017-09-29 23:59                     ` Zhang, Tina
2017-10-06 12:12                       ` Gerd Hoffmann
2017-10-07  7:39                         ` Zhang, Tina
2017-09-29  7:32   ` Gerd Hoffmann
2017-08-18 10:21 ` [PATCH v14 6/7] drm/i915: Introduce GEM proxy Tina Zhang
2017-08-18 11:36   ` Joonas Lahtinen
2017-08-18 10:21 ` [PATCH v14 7/7] drm/i915/gvt: Dmabuf support for GVT-g Tina Zhang
2017-08-18 12:19 ` ✓ Fi.CI.BAT: success for drm/i915/gvt: Dma-buf " Patchwork
2017-08-25 11:47 ` [PATCH v14 0/7] " Gerd Hoffmann
2017-08-25 12:52   ` Wang, Zhi A
2017-09-04  6:23     ` Zhang, Tina
2017-09-04  6:38       ` Gerd Hoffmann

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