[PATCH] drm/amdkfd: fix the wrong no space return while acquires packet buffer

[PATCH] drm/amdkfd: fix the wrong no space return while acquires packet buffer

[Huang Rui]

The queue buffer index starts from position 0, so the available buffer size
which starts from position 0 to rptr should be "rptr" index value. While the
packet_size_in_dwords == rptr, the available buffer is just good enough.

Signed-off-by: Huang Rui <ray.huang@amd.com>
---
 drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c b/drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c
index bae7064..4667c8f 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c
@@ -263,7 +263,7 @@ int kq_acquire_packet_buffer(struct kernel_queue *kq,
 		/* make sure after rolling back to position 0, there is
 		 * still enough space.
 		 */
-		if (packet_size_in_dwords >= rptr)
+		if (packet_size_in_dwords > rptr)
 			goto err_no_space;
 
 		/* fill nops, roll back and start at position 0 */
-- 
2.7.4

_______________________________________________
amd-gfx mailing list
amd-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/amd-gfx

Re: [PATCH] drm/amdkfd: fix the wrong no space return while acquires packet buffer

[Pan, Xinhui]

> 2020年3月19日 18:51，Huang Rui <ray.huang@amd.com> 写道：
> 
> The queue buffer index starts from position 0, so the available buffer size
> which starts from position 0 to rptr should be "rptr" index value. While the
> packet_size_in_dwords == rptr, the available buffer is just good enough.
> 
> Signed-off-by: Huang Rui <ray.huang@amd.com>
> ---
> drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c b/drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c
> index bae7064..4667c8f 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c
> @@ -263,7 +263,7 @@ int kq_acquire_packet_buffer(struct kernel_queue *kq,
> 		/* make sure after rolling back to position 0, there is
> 		 * still enough space.
> 		 */
> -		if (packet_size_in_dwords >= rptr)
> +		if (packet_size_in_dwords > rptr)

rptr should always be > wptr unless ring is empty.

say, rptr is 4, packet_size_in_dwords is 4. Then wptr changes from 0 to 4, that is illegal.


> 			goto err_no_space;
> 
> 		/* fill nops, roll back and start at position 0 */
> -- 
> 2.7.4
> 
> _______________________________________________
> amd-gfx mailing list
> amd-gfx@lists.freedesktop.org
> https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.freedesktop.org%2Fmailman%2Flistinfo%2Famd-gfx&amp;data=02%7C01%7Cxinhui.pan%40amd.com%7Cdb98cfd84b764e77d20e08d7cbf38dff%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637202119950119907&amp;sdata=mqrl2uooQ95Dns4l6CtmmOBCm%2FqZyw1pX48VA20mlZY%3D&amp;reserved=0

_______________________________________________
amd-gfx mailing list
amd-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/amd-gfx

Re: [PATCH] drm/amdkfd: fix the wrong no space return while acquires packet buffer

[Huang Rui]

On Thu, Mar 19, 2020 at 07:42:04PM +0800, Pan, Xinhui wrote:
> 
> 
> > 2020年3月19日 18:51，Huang Rui <ray.huang@amd.com> 写道：
> > 
> > The queue buffer index starts from position 0, so the available buffer size
> > which starts from position 0 to rptr should be "rptr" index value. While the
> > packet_size_in_dwords == rptr, the available buffer is just good enough.
> > 
> > Signed-off-by: Huang Rui <ray.huang@amd.com>
> > ---
> > drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c b/drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c
> > index bae7064..4667c8f 100644
> > --- a/drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c
> > +++ b/drivers/gpu/drm/amd/amdkfd/kfd_kernel_queue.c
> > @@ -263,7 +263,7 @@ int kq_acquire_packet_buffer(struct kernel_queue *kq,
> > 		/* make sure after rolling back to position 0, there is
> > 		 * still enough space.
> > 		 */
> > -		if (packet_size_in_dwords >= rptr)
> > +		if (packet_size_in_dwords > rptr)
> 
> rptr should always be > wptr unless ring is empty.
> 
> say, rptr is 4, packet_size_in_dwords is 4. Then wptr changes from 0 to 4, that is illegal.
> 

Hey, xinhui, yes. :-)

See the comment "we can only use up to queue_size_dword - 1 dwords", that
we cannot use the whole packet slots in the queue, it's to differentiate
empty and full cases.

Thanks,
Ray

> 
> > 			goto err_no_space;
> > 
> > 		/* fill nops, roll back and start at position 0 */
> > -- 
> > 2.7.4
> > 
> > _______________________________________________
> > amd-gfx mailing list
> > amd-gfx@lists.freedesktop.org
> > https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Flists.freedesktop.org%2Fmailman%2Flistinfo%2Famd-gfx&amp;data=02%7C01%7Cxinhui.pan%40amd.com%7Cdb98cfd84b764e77d20e08d7cbf38dff%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637202119950119907&amp;sdata=mqrl2uooQ95Dns4l6CtmmOBCm%2FqZyw1pX48VA20mlZY%3D&amp;reserved=0
> 
_______________________________________________
amd-gfx mailing list
amd-gfx@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/amd-gfx