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

[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;