[Nouveau] Documentation request for MP warp error 0x10

[Ilia Mirkin]

Hi Robert,

Thanks for the quick response! That goes in line with my observations
which is that these things happen when using an ATOM/RED instruction.
I've checked and rechecked that I'm generating ops with identical bits
as what the proprietary driver does, however (and nvdisasm prints
identical output). Could you advise what the proper way of indicating
that the memory is "global" to the op? I'm sure I'm just missing
something simple. If you show me what to look for in SM35 I can
probably find it on my own for SM20/SM30/SM50.

In case you're interested in looking at the mesa code, It's available
on my atomic2 branch at:
https://github.com/imirkin/mesa/commits/atomic2 . However I hardly
expect you to debug my buggy code :) The SUREDP stuff is about surface
RED ops, the existing code uses it but I'm going to leave it for image
support and break direct buffer accesses directly into OP_ATOM (and in
NVIDIA terminology RED is just ATOM without a destination).

Thanks,

  -ilia

On Fri, Oct 2, 2015 at 5:48 PM, Robert Morell <rmorell at nvidia.com> wrote:
> Hi Ilia,
>
> Error 0x10 is INVALID_ADDR_SPACE. It is triggered when an ATOM or RED [1]
> instruction accesses local or shared memory. Global memory accesses are the
> only allowed accesses for ATOM and RED instructions.
>
>
> Note that SM30 also has this restriction that ATOM and RED should only be used
> on global memory, but it is not error-checked in hardware until SM35.
>
>
> [1] What is documented as RED internally appears to be called SUREDP in Mesa.
>
>
> - Robert
>
> On Wed, Sep 30, 2015 at 03:14:47PM -0400, Ilia Mirkin wrote:
>> Hello,
>>
>> I've recently come across an error reported by the GPU and would like
>> to know what it means and especially what causes it to be triggered.
>> Any information would be very useful:
>>
>> I'm seeing MP warp error 0x10 (appears in MP register 0x48). This is
>> what we currently have in nouveau:
>>
>> <reg32 offset="0x048" name="TRAP_WARP_ERROR"> <!-- ctx-switched -->
>> <bitfield high="15" low="0" name="ID">
>> <value value="1" name="STACK_MISMATCH"/>
>> <value value="5" name="MISALIGNED_PC"/>
>> <value value="8" name="MISALIGNED_GPR"/>
>> <value value="9" name="INVALID_OPCODE"/>
>> <value value="13" name="GPR_OUT_OF_BOUNDS"/>
>> <value value="14" name="MEM_OUT_OF_BOUNDS"/>
>> <value value="17" name="INVALID_PARAM"/>
>> </bitfield>
>> </reg32>
>>
>> [Additionally it seems like 15 = UNALIGNED_MEM_ACCESS]
>>
>> It seems to happen whenever I try to access global memory on kepler
>> (potentially only atomics, not sure at this point). Knowing precisely
>> what causes the error to get triggered (and esp what we need to do in
>> order not to trigger it) would be most useful.
>>
>> For reference, my shader looks something like this (for SM35):
>>
>>         /*0018*/                   LDC.64 R0, c[0xf][0x1c0];
>>   /* 0x7ca80780e01ffc02 */
>>         /*0020*/                   ATOM.E.ADD R2, [R0], R2;
>>   /* 0x68080000011c000a */
>>         /*0028*/                   LD.E.CG R0, [R0];
>>   /* 0xcc800000001c0000 */
>>
>> I know that the proprietary drivers are a lot more sophisticated and
>> only do the atomic add from a single lane, but I was assuming that was
>> not required.
>>
>> Thanks,
>>
>>   -ilia
>>