From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Anholt Subject: Re: I've got the RC6 bug Date: Wed, 18 Jan 2012 09:51:30 -0800 Message-ID: <87lip4ew65.fsf@eliezer.anholt.net> References: <20120116163338.GA3627@phenom.ffwll.local> <20120118002426.GB4093@phenom.ffwll.local> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============0276927847==" Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org Errors-To: intel-gfx-bounces+gcfxdi-intel-gfx=m.gmane.org@lists.freedesktop.org To: Chris Wilson , Daniel Vetter , CC Cc: intel-gfx@lists.freedesktop.org, Ben Widawsky List-Id: intel-gfx@lists.freedesktop.org --===============0276927847== Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha1; protocol="application/pgp-signature" --=-=-= Content-Transfer-Encoding: quoted-printable On Wed, 18 Jan 2012 11:17:52 +0000, Chris Wilson = wrote: > On Wed, 18 Jan 2012 01:24:26 +0100, Daniel Vetter wrote: > > On Wed, Jan 18, 2012 at 01:16:02AM +0100, CC wrote: > > > I attached the error state. > >=20 > > Nice one, your gpu seems to have simply disappeared. And the ringbuffer > > contains a rather peculiar cmd sequence. Putting Chris (maybe he > > recognizes the pattern) and Ben (he's got a patch in the works to dump a > > debug register that might be interesting here) on cc. It's too late atm > > for me to think about this some more. >=20 > Not simply disappeared, someone clobbered it with an extremely large > hammer. The GPU was killed by a stray write to address 0 which took out > the render ring buffer and its hws page. So my first thought is a > missing relocation, and i965g springs to mind. > -Chris At one point there was a bug in Mesa that wrote to 0: commit dfada714f8db3deea2fea3583c3c166a78db1117 Author: Eric Anholt Date: Fri Jun 17 18:20:36 2011 -0700 i965/gen6: Use an BO instead of writing to address 0 for PIPE_CONTROL W= /A. =20=20=20=20 This was spectacularly unsafe. On my system, address 0 happens to be the hardware status page for the render ring, and the first quadword of that happens to contain nothing we ever look at, but I sure didn't look forward to having to debug some day when, for example, the kernel happened to bind the ringbuffer before binding the hwsp. --=-=-= Content-Type: application/pgp-signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) iEYEARECAAYFAk8XBqIACgkQHUdvYGzw6vcBMgCgiq6oozkKu/I0kyfDVyb0GBSR PAMAoJgM6ud3kkm8oJO6Ayyzif7JYyJn =HQHl -----END PGP SIGNATURE----- --=-=-=-- --===============0276927847== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/intel-gfx --===============0276927847==--