[PATCH 3/3] drm/amdgpu: Fix multi-level page table bugs for large BOs

[Christian König]

Am 29.03.2017 um 16:46 schrieb Michel Dänzer:
> On 29/03/17 11:32 PM, Felix Kuehling wrote:
>> On 17-03-29 02:52 AM, Christian König wrote:
>>> Please clean that up and also remove all those WARN_ON(), we don't
>>> want to spam the system log with backtraces like this.
>> I disagree. When you see the backtraces from WARN_ONs in
>> amdgpu_vm_get_pt, it means the driver is trying to update a page table
>> that hasn't been allocated. Without those WARN_ONs there is absolutely
>> no warning of any kind - amdgpu_vm_update_pte just fails silently (it's
>> a void function).
>>
>> Therefore I wouldn't call those warnings spam. Given that the VM PT
>> allocation code for multi-levels is non-trivial, I think that's a good
>> sanity check to have and really helpful to see in a log when user report
>> random VM faults.
> WARN_ON_ONCE might be a compromise. We'll still get a backtrace, but it
> won't cause crazy log spam if the bad condition is consistently hit.
Good idea. We should also only add one at the beginning of the function 
and not multiple catches for each dependent variable.

Regards,
Christian.