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From: Pekka Paalanen <ppaalanen@gmail.com>
To: Daniel Vetter <daniel@ffwll.ch>
Cc: Sean Paul <sean@poorly.run>,
	dri-devel@lists.freedesktop.org, Dave Airlie <airlied@redhat.com>
Subject: Re: [PATCH] drm/doc: device hot-unplug for userspace
Date: Mon, 1 Jun 2020 15:04:38 +0300	[thread overview]
Message-ID: <20200601150438.5833f021@eldfell.localdomain> (raw)
In-Reply-To: <20200528144545.GU206103@phenom.ffwll.local>


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On Thu, 28 May 2020 16:45:45 +0200
Daniel Vetter <daniel@ffwll.ch> wrote:

> On Thu, May 28, 2020 at 03:27:57PM +0300, Pekka Paalanen wrote:

...

> > Hmm. Maybe Wayland compositors should ignore all EGL import failures
> > that happen after the wl_buffer has been created (which implies that
> > the dmabuf has been validated to work initially). When import fails at
> > a later time, the compositor should just paint some error pattern
> > instead of the window. That would let the kernel keep on returning
> > errors.
> > 
> > Yeah, ok. I'll keep the ENODEV there in my next version. Let's see how
> > that looks then.  
> 
> tbh I have no idea what to do with dma-buf shared across drivers.
> 
> For dma-fence it's fairly simple: Force-complete them all, with an error
> code of ENODEV. But for dma-buf I have no idea. As long as the dma-buf
> sits in system memory it should keep working, plus/minus bugs in the
> exporter where it tries to look at device state that might no longer be
> there.
> 
> The real fun starts when the buffer is in vram, or when the mmap somehow
> goes through the device (but that's more a case for integrated gpu, and
> it's a bit hard to hotunplug those and consider that a real use-case).

Is forced driver unbind not a real use-case, or would it not invalidate
the memory references wrapped in a dmabuf?

In the proposal, I listed driver unbind as a use-case.

I don't mind if cross-driver shared dmabuf needed ten years of kernel
internals development to reach a state where it won't explode anymore,
but that's the goal I want to set today. I don't think we can tell
userspace to never share dmabufs cross-device if the exporter device is
hot-unpluggable, can we?


Thanks,
pq

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  reply	other threads:[~2020-06-01 12:04 UTC|newest]

Thread overview: 44+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-19 10:06 [PATCH] drm/doc: device hot-unplug for userspace Pekka Paalanen
2020-05-19 14:37 ` Andrey Grodzovsky
2020-05-20 11:19   ` Pekka Paalanen
2020-05-20 12:46     ` Daniel Vetter
2020-05-20 14:50       ` Andrey Grodzovsky
2020-05-25 12:13         ` Andrey Grodzovsky
2020-05-25 14:28         ` Daniel Vetter
2020-05-25 14:55           ` Pekka Paalanen
2020-05-25 15:09             ` Daniel Vetter
2020-05-28 12:27               ` Pekka Paalanen
2020-05-28 14:45                 ` Daniel Vetter
2020-06-01 12:04                   ` Pekka Paalanen [this message]
2020-05-20 12:55 ` Daniel Vetter
2020-05-20 13:20   ` Simon Ser
2020-05-20 14:19     ` Daniel Vetter
2020-05-22  9:54       ` Pekka Paalanen
2020-05-25 14:29         ` Daniel Vetter
2020-05-25 12:46 ` [PATCH v2] " Pekka Paalanen
2020-05-25 13:51   ` Andrey Grodzovsky
2020-05-25 14:30     ` Daniel Vetter
2020-05-25 15:02       ` Pekka Paalanen
2020-05-25 14:41     ` Pekka Paalanen
2020-05-26 14:30 ` [PATCH] " Andrey Grodzovsky
2020-05-27  6:44   ` Pekka Paalanen
2020-05-27 13:51     ` Andrey Grodzovsky
2020-05-27 14:39       ` Daniel Vetter
2020-05-27 15:23         ` Andrey Grodzovsky
2020-05-27 19:44           ` Christian König
2020-05-27 20:25             ` Daniel Vetter
2020-05-28 12:13               ` Pekka Paalanen
2020-05-28 21:28               ` Andrey Grodzovsky
2020-06-01 14:32 ` [PATCH v3] " Pekka Paalanen
2020-06-02 14:00   ` Andrey Grodzovsky
2020-06-03  8:19     ` Daniel Vetter
2020-06-08 16:05   ` Pekka Paalanen
2020-06-10 15:40   ` Daniel Vetter
2020-06-22 14:05 ` [PATCH v4] " Pekka Paalanen
2020-06-22 16:56   ` Alex Deucher
2020-06-27 10:02   ` Noralf Trønnes
2020-07-07 11:38 ` [PATCH v5] " Pekka Paalanen
2020-07-07 11:49   ` Karol Herbst
2020-07-07 12:13     ` Daniel Vetter
2020-07-07 12:59   ` Simon Ser
2020-07-30 13:35   ` drm/doc: missing SPDX license identifier (Was: Re: [PATCH v5] drm/doc: device hot-unplug for userspace) Emil Velikov

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