[Intel-gfx] [RFCv3 10/15] drm/i915: update PDPs by condition when submit the LRC context

[Wang, Zhi A]

OK. I will see. :) Thanks for the comments. 

-----Original Message-----
From: Chris Wilson [mailto:chris at chris-wilson.co.uk] 
Sent: Friday, March 11, 2016 7:28 PM
To: Wang, Zhi A
Cc: intel-gfx at lists.freedesktop.org; igvt-g at lists.01.org; Tian, Kevin; Lv, Zhiyuan; Niu, Bing; Song, Jike; daniel.vetter at ffwll.ch; Cowperthwaite, David J; joonas.lahtinen at linux.intel.com
Subject: Re: [RFCv3 10/15] drm/i915: update PDPs by condition when submit the LRC context

On Fri, Mar 11, 2016 at 06:59:41PM +0800, Zhi Wang wrote:
> Previously the PDPs inside the ring context will be updated
> 
> - When populating a LRC context
> - Before submitting a LRC context (only for 32 bit PPGTT, as the amount
> of used PDPs may be changed during PPGTT page table grow)
> 
> Under GVT-g, each VM owns a GVT context used as the shadow context. When
> guest submits a context, GVT-g will load guest context into the GVT
> context, and submit this context to i915 GEM submission system.
> 
> So this GVT context could be used by different guest context, and the
> PPGTT root pointer in guest contexts might be different as well, if guest
> is using full PPGTT mode.
> 
> In current i915, the root pointer in a LRC context will only be updated
> during the LRC context creation.
> 
> This patch postpones the root pointer upgrade to the time of submission,
> which will give GVT-g a chance to reload a new PPGTT page table root
> pointer into an existing GVT context.

Not explained is why you cannot use the existing dirty flags.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre