On Sun, Aug 19, 2012 at 11:02:00PM +0200, Marcin Slusarz wrote:
> Commit "drm/nouveau: port all engines to new engine module format" changed
> IB size calculation to be less wasteful, but didn't take into account already
> existing off-by-one bugs :).
> 
> So:
> - ib_max is the last entry, so we need to +1 when calculating number of
>   free entries
> - nv50_dma_wait already does +1 (for FIRE_RING), so we don't need another +1
>   on nouveau_gem_ioctl_pushbuf side
> - there are 512 allocated IB entries (and it needs to be round number), so we
>   can accept at most 511 entries from userspace (we need one for FIRE_RING) -
>   fortunately userspace already flushes at 511, so nr_push check change won't
>   have any impact
Also skipped this patch for now as I have work in progress that will improve 
this and
related code.  I should have it in the tree soon.

> 
> Signed-off-by: Marcin Slusarz <[email protected]>
> ---
>  drivers/gpu/drm/nouveau/nouveau_chan.c |    2 +-
>  drivers/gpu/drm/nouveau/nouveau_dma.c  |    2 +-
>  drivers/gpu/drm/nouveau/nouveau_gem.c  |    4 ++--
>  3 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/gpu/drm/nouveau/nouveau_chan.c 
> b/drivers/gpu/drm/nouveau/nouveau_chan.c
> index fd15ebf..d0c0271 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_chan.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_chan.c
> @@ -318,7 +318,7 @@ nouveau_channel_init(struct nouveau_channel *chan, u32 
> vram, u32 gart)
>               chan->dma.ib_base =  0x10000 / 4;
>               chan->dma.ib_max  = (0x01000 / 8) - 1;
>               chan->dma.ib_put  = 0;
> -             chan->dma.ib_free = chan->dma.ib_max - chan->dma.ib_put;
> +             chan->dma.ib_free = chan->dma.ib_max - chan->dma.ib_put + 1;
>               chan->dma.max = chan->dma.ib_base;
>               break;
>       }
> diff --git a/drivers/gpu/drm/nouveau/nouveau_dma.c 
> b/drivers/gpu/drm/nouveau/nouveau_dma.c
> index 40f91e1..e814fab 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_dma.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_dma.c
> @@ -128,7 +128,7 @@ nv50_dma_push_wait(struct nouveau_channel *chan, int 
> count)
>  
>               chan->dma.ib_free = get - chan->dma.ib_put;
>               if (chan->dma.ib_free <= 0)
> -                     chan->dma.ib_free += chan->dma.ib_max;
> +                     chan->dma.ib_free += chan->dma.ib_max + 1;
>       }
>  
>       return 0;
> diff --git a/drivers/gpu/drm/nouveau/nouveau_gem.c 
> b/drivers/gpu/drm/nouveau/nouveau_gem.c
> index 6454370..d19c7aa 100644
> --- a/drivers/gpu/drm/nouveau/nouveau_gem.c
> +++ b/drivers/gpu/drm/nouveau/nouveau_gem.c
> @@ -662,7 +662,7 @@ nouveau_gem_ioctl_pushbuf(struct drm_device *dev, void 
> *data,
>       if (unlikely(req->nr_push == 0))
>               goto out_next;
>  
> -     if (unlikely(req->nr_push > NOUVEAU_GEM_MAX_PUSH)) {
> +     if (unlikely(req->nr_push >= NOUVEAU_GEM_MAX_PUSH)) {
>               NV_ERROR(drm, "pushbuf push count exceeds limit: %d max %d\n",
>                        req->nr_push, NOUVEAU_GEM_MAX_PUSH);
>               return nouveau_abi16_put(abi16, -EINVAL);
> @@ -718,7 +718,7 @@ nouveau_gem_ioctl_pushbuf(struct drm_device *dev, void 
> *data,
>       }
>  
>       if (chan->dma.ib_max) {
> -             ret = nouveau_dma_wait(chan, req->nr_push + 1, 16);
> +             ret = nouveau_dma_wait(chan, req->nr_push, 16);
>               if (ret) {
>                       NV_ERROR(drm, "nv50cal_space: %d\n", ret);
>                       goto out;
> -- 
> 1.7.8.6
> 
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