[Intel-gfx] [PATCH 3/3] i965: check scratch page in a locked fashion on each ioctl

[Rogovin, Kevin]

Thanks, I will make a v2 and post it shortly to correct for my terribly embarrassing omission caused by even more terribly embarrassing ignorance.

-Kevin

-----Original Message-----
From: Chris Wilson [mailto:chris at chris-wilson.co.uk] 
Sent: Tuesday, December 5, 2017 12:39 PM
To: Rogovin, Kevin <kevin.rogovin at intel.com>; intel-gfx at lists.freedesktop.org
Subject: RE: [Intel-gfx] [PATCH 3/3] i965: check scratch page in a locked fashion on each ioctl

Quoting Rogovin, Kevin (2017-12-05 10:30:04)
> Hi,
> 
> > Per context, then you can remove the locking. It's fitting since the scratch page is per-context anyway.
> 
>  The scratch page is per context? This I did not know, I thought it was per PPGTT. If that is the case, then my proposed interface to get/set the scratch page contents is wrong because it does not pass the HW context id.

Yes, it per-vm, which is per-ctx on everything you want to investigate on. gen4-7 it is a global GTT with a global scratch, and just a mutex inside one process is not going to give you atomicity.
-Chris