linux-kernel - Re: [Spice-devel] [PATCH] Revert "drm/qxl: drop prime import/export callbacks"

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Message-ID: <20190429143757.yljjfsgobhi23xnb@sirius.home.kraxel.org>
Date:   Mon, 29 Apr 2019 16:37:57 +0200
From:   Gerd Hoffmann <kraxel@...hat.com>
To:     Daniel Vetter <daniel@...ll.ch>
Cc:     David Airlie <airlied@...ux.ie>,
        open list <linux-kernel@...r.kernel.org>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        "open list:DRM DRIVER FOR QXL VIRTUAL GPU" 
        <virtualization@...ts.linux-foundation.org>,
        David Airlie <airlied@...hat.com>,
        "open list:DRM DRIVER FOR QXL VIRTUAL GPU" 
        <spice-devel@...ts.freedesktop.org>
Subject: Re: [Spice-devel] [PATCH] Revert "drm/qxl: drop prime import/export
 callbacks"

  Hi,

> > More useful would be some way to signal this self-reimport capability
> > to userspace somehow.  See DRM_PRIME_CAP_LOCAL patch.
> 
> Userspace is supposed to test whether import/export works for a
> specific combo, not blindly assume it does and then keel over. I think
> we need to fix that, not add more flags - there's lots of reasons why
> a given pair of devices can't share buffers (e.g. all the contiguous
> allocations stuff on socs).

Ok.  Lets scratch the DRM_PRIME_CAP_LOCAL idea then and blame userspace
instead.

> > Right now I have the choice to set DRM_PRIME_CAP_{IMPORT,EXPORT}, in
> > which case some userspace assumes it can do cross-driver export/import
> > and trips over that not working.  Or I do not set
> > DRM_PRIME_CAP_{IMPORT,EXPORT}, which breaks DRI3 ...
> 
> Yeah that's not an option.

Good.  Can I get an ack for this patch then, as it unbreaks DRI3 with qxl?

thanks,
  Gerd