linux-kernel - Re: Intel 965G: i915_dispatch_cmdbuffer failed (2.6.19-rc2)

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Date:	Fri, 20 Oct 2006 12:43:44 +0100
From:	Keith Whitwell <keith@...gstengraphics.com>
To:	Ryan Richter <ryan@....solarneutrino.net>
CC:	Keith Packard <keithp@...thp.com>, dri-devel@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org
Subject: Re: Intel 965G: i915_dispatch_cmdbuffer failed (2.6.19-rc2)

Ryan Richter wrote:
> On Wed, Oct 18, 2006 at 07:54:41AM +0100, Keith Whitwell wrote:
>> This is all a little confusing as the driver doesn't really use that 
>> path in normal operation except for a single command - MI_FLUSH, which 
>> is shared between the architectures.  In normal operation the hardware 
>> does the validation for us for the bulk of the command stream.  If there 
>>  were missing functionality in that ioctl, it would be failing 
>> everywhere, not just in this one case.
>>
>> I guess the questions I'd have are
>> 	- did the driver work before the kernel upgrade?
>> 	- what path in userspace is seeing you end up in this ioctl?
>> 	- and like Keith, what commands are you seeing?
>>
>> The final question is interesting not because we want to extend the 
>> ioctl to cover those, but because it will give a clue how you ended up 
>> there in the first place.
> 
> Here's a list of all the failing commands I've seen so far:
> 
> 3a440003
> d70003
> 2d010003
> e5b90003
> 2e730003
> 8d8c0003
> c10003
> d90003
> be0003
> 1e3f0003

Ryan,

Those don't look like any commands I can recognize.  I'm still confused 
how you got onto this ioctl in the first place - it seems like something 
pretty fundamental is going wrong somewhere.  What would be useful to me 
is if you can use GDB on your application and get a stacktrace for how 
you end up in this ioctl in the cases where it is failing?

Additionally, if you're comfortable doing this, it would be helpful to 
see all the arguments that userspace thinks its sending to the ioctl, 
compared to what the kernel ends up thinking it has to validate.  There 
shouldn't ever be more than two dwords being validated at a time, and 
they should look more or less exactly like {0x02000003, 0}, and be 
emitted from bmSetFence().

All of your other wierd problems, like the assert failures, etc, make me 
wonder if there just hasn't been some sort of build problem that can 
only be resolved by clearing it out and restarting.

It wouldn't hurt to just nuke your current Mesa and libdrm builds and 
start from scratch - you'll probably have to do that to get debug 
symbols for gdb anyway.

Keith
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