Re: [PATCH] Revert "drm/i915: Allocate context objects from stolen"

From: Akash Goel <akash.goel@intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>
Cc: ankitprasad.r.sharma@intel.com, intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH] Revert "drm/i915: Allocate context objects from stolen"
Date: Tue, 30 Jun 2015 12:07:06 +0530	[thread overview]
Message-ID: <1435646226.20771.140.camel@akashgoe-desktop> (raw)
In-Reply-To: <20150629200537.GA26189@nuc-i3427.alporthouse.com>

On Mon, 2015-06-29 at 21:05 +0100, Chris Wilson wrote:
> On Mon, Jun 29, 2015 at 08:53:12PM +0100, Chris Wilson wrote:
> > On Mon, Jun 29, 2015 at 08:28:35PM +0300, ville.syrjala@linux.intel.com wrote:
> > > From: Ville Syrjälä <ville.syrjala@linux.intel.com>
> > > 
> > > Stolen gets trashed during hibernation, so storing contexts there
> > > is not a very good idea. On my IVB machines this leads to a totally
> > > dead GPU on resume. A reboot is required to resurrect it. So let's
> > > not store contexts where they will get trampled.
> > 
> > We need to disable use of stolen entirely then. Fortunately ring buffers
> > are idle (and so trashable), but all plans for actually using stolen are
> > off the cards then (e.g. the create2 request to allocate from stolen).
> > 
> > I think it is fairer to say that stolen memory is not restored, and to
> > do so for hibernation of non-volatile objects would require allocation
> > of ordinary buffers. Ack on the patch in the short term, does a long
> > term plan of migrating I915_MADV_WILLNEED stolen objects to normal
> > memory on hibernation sound acceptable? (I don't like how it makes
> > hibernation special in terms of shutdown/suspend, but meh)
> 
> I can get a patch to do the migration ready tomorrow, though it will
> certainly be quite a few interesting patches.
> 
Hi Chris,

Thanks for keeping us in the loop. 
As you are aware, that we started working on the patches for utilizing
the Stolen area, based on the placement preference flag passed by the
User (extended gem_create ioctl for it). We are trying to get them
reviewed. Would this use case of hibernation thwart that efforts ?

Are you planning to add the support for taking the back up of the
objects allocated from Stolen memory area, by copying them to shmem at
the time of hibernation. Should the objects be copied back to Stolen
area on resume ? 
Is this something, which we can implement and add a new patch to the
series ? 

Best regards
Akash

> What's the timeframe for a fix/revert here? (i.e. did this get merged
> for 4.2 or was it 4.3?)
> -Chris

> 

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