[PATCH 2/2] drm/amdgpu:256dw is enough for one ib_schedule

[Christian König]

True indeed. Something like 256 + 32 * num_ibs (or even 16 * num_ibs??? 
Need to double check) should do as well.

Christian.

Am 25.08.2016 um 10:28 schrieb Liu, Monk:
> But even user space will submit 10 ibs this submission, the calculate of 256*ibs is totally overflow, remember that ring buffer is only 4kb size
>
> -----Original Message-----
> From: Christian König [mailto:deathsimple at vodafone.de]
> Sent: Thursday, August 25, 2016 4:12 PM
> To: Liu, Monk <Monk.Liu at amd.com>; amd-gfx at lists.freedesktop.org
> Subject: Re: [PATCH 2/2] drm/amdgpu:256dw is enough for one ib_schedule
>
> Well userspace is allowed to send any number of IBs down to this if I remember correctly.
>
> So we clearly need something depending on the number of IBs or reject submissions with to many IBs earlier in the CS.
>
> Otherwise we clearly open up a possible problem where userspace can trigger a ring overrun.
>
> Regards,
> Christian.
>
> Am 25.08.2016 um 07:58 schrieb Monk Liu:
>> Change-Id: I1ee3258276868a753e536ae2d9ae1b12e7eaf791
>> Signed-off-by: Monk Liu <Monk.Liu at amd.com>
>> ---
>>    drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c | 2 +-
>>    1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c
>> b/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c
>> index 4e5b2f3..b82904c 100644
>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c
>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ib.c
>> @@ -151,7 +151,7 @@ int amdgpu_ib_schedule(struct amdgpu_ring *ring, unsigned num_ibs,
>>    		return -EINVAL;
>>    	}
>>    
>> -	r = amdgpu_ring_alloc(ring, 256 * num_ibs);
>> +	r = amdgpu_ring_alloc(ring, 256);
>>    	if (r) {
>>    		dev_err(adev->dev, "scheduling IB failed (%d).\n", r);
>>    		return r;
>