Re: [PATCH 3/7] drm/i915: don't allocate fbcon from stolen memory if it's too big

Chris Wilson
2015-09-28T09:09:24Z

On Mon, Sep 28, 2015 at 10:54:59AM +0200, Daniel Vetter wrote:
> On Wed, Sep 23, 2015 at 05:54:25PM +0100, Chris Wilson wrote:
> > On Wed, Sep 23, 2015 at 12:52:23PM -0300, Paulo Zanoni wrote:
> > > Technology has evolved and now we have eDP panels with 3200x1800
> > > resolution. In the meantime, the BIOS guys didn't change the default
> > > 32mb for stolen memory. On top of that, we can't assume our users will
> > > be able to increase the default stolen memory size to more than 32mb -
> > > I'm not even sure all BIOSes allow that.
> >
> > fbcon is just a small part of the problem, we can trivially fill stolen
> > with kernel objects even before we let userspace at it. I agree that being
> > able to prioritise allocation to HW functions is good, but it is not that hard
> > to write an eviction + migration pass - given that we already have large
> > chunks of that written. The only issue is that (at least the sketch I
> > have in mind) will only evict objects so if we have fragmentation
> > caused by HW functions, allocations can still fail.
>
> Problem with fbcon is that we can migrate it (well we could do _really_

Can or can't? The screen.base pointer is an iomap so to migrate it we
just need to point the PTE elsewhere. We can't combine a vmalloc arena
and stolen anyway :|
-Chris

--
Chris Wilson, Intel Open Source Technology Centre