Re: [PATCH v3] drm/amdgpu: skip xcp drm device allocation when out of drm resource

"Lazar, Lijo" <lijo.lazar@xxxxxxx> · Sat, 12 Aug 2023 22:30:20 +0530

On 8/12/2023 6:14 PM, James Zhu wrote:

On 2023-08-11 21:39, Lazar, Lijo wrote:

[AMD Official Use Only - General]


A dynamic partition switch could happen later.  The switch could still 
be successful in terms of hardware,
[JZ] Only ignore render node assignment, and remove visibility in user 
space, xcp continues to be generated as usual. so switch should work as 
usual

Switch is not useful for the user unless the apps can make use of the 
render nodes. A 'success' from hardware perspective doesn't turn out to 
be a 'success' for users eventually to make use of the extra partition.

and hence gives a false feeling of success even if there are no render 
nodes available for any app to make use of the partition.
[JZ] from driver prospective, the switch is real success, treat the last 
one harvested in user space.. there is warning in kernel log, and final 
solution for more than 64 nodes is on-going

The render nodes are allocated during driver load and the message will 
go unnoticed. We could still allow the switch, but the message should be 
there during a partition switch like 'only x/y (x out of y nodes) are 
usable'. The worst case is - only 1 out of N meaning no benefit - and in 
that case user may switch back to normal mode to make use of full 
compute power.


Also, a kfd node is not expected to have a valid xcp pointer on 
devices without partition.
[JZ] won't affect xcp pointer, only ddev.
This access could break then gpu->xcp->ddev.
[JZ] added skip when ddev==NULL

What I meant is xcp in kfd node could be NULL on SOCs like NV series. 
There should be a check for xcp before accessing ddev -
https://elixir.bootlin.com/linux/v6.5-rc5/source/drivers/gpu/drm/amd/amdkfd/kfd_device.c#L794

Thanks,
Lijo


Thanks,
Lijo
------------------------------------------------------------------------
*From:* amd-gfx <amd-gfx-bounces@xxxxxxxxxxxxxxxxxxxxx> on behalf of 
James Zhu <James.Zhu@xxxxxxx>
*Sent:* Saturday, August 12, 2023 2:36:27 AM
*To:* amd-gfx@xxxxxxxxxxxxxxxxxxxxx <amd-gfx@xxxxxxxxxxxxxxxxxxxxx>
*Cc:* Lin, Amber <Amber.Lin@xxxxxxx>; Zhu, James <James.Zhu@xxxxxxx>; 
Kasiviswanathan, Harish <Harish.Kasiviswanathan@xxxxxxx>; Koenig, 
Christian <Christian.Koenig@xxxxxxx>
*Subject:* [PATCH v3] drm/amdgpu: skip xcp drm device allocation when 
out of drm resource
Return 0 when drm device alloc failed with -ENOSPC in
order to  allow amdgpu drive loading. But the xcp without
drm device node assigned won't be visiable in user space.
This helps amdgpu driver loading on system which has more
than 64 nodes, the current limitation.

The proposal to add more drm nodes is discussed in public,
which will support up to 2^20 nodes totally.
kernel drm:
https://lore.kernel.org/lkml/20230724211428.3831636-1-michal.winiarski@xxxxxxxxx/T/
libdrm:
https://gitlab.freedesktop.org/mesa/drm/-/merge_requests/305

Signed-off-by: James Zhu <James.Zhu@xxxxxxx>
Acked-by: Christian König <christian.koenig@xxxxxxx>

-v2: added warning message
-v3: use dev_warn
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_xcp.c   | 13 ++++++++++++-
 drivers/gpu/drm/amd/amdkfd/kfd_topology.c | 10 +++++++++-
 2 files changed, 21 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_xcp.c 
b/drivers/gpu/drm/amd/amdgpu/amdgpu_xcp.c
index 9c9cca129498..565a1fa436d4 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_xcp.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_xcp.c
@@ -239,8 +239,13 @@ static int amdgpu_xcp_dev_alloc(struct 
amdgpu_device *adev)

         for (i = 1; i < MAX_XCP; i++) {
                 ret = amdgpu_xcp_drm_dev_alloc(&p_ddev);
-               if (ret)
+               if (ret == -ENOSPC) {
+                       dev_warn(adev->dev,
+                       "Skip xcp node #%d when out of drm node 
resource.", i);
+                       return 0;
+               } else if (ret) {
                         return ret;
+               }

                 /* Redirect all IOCTLs to the primary device */
                 adev->xcp_mgr->xcp[i].rdev = p_ddev->render->dev;
@@ -328,6 +333,9 @@ int amdgpu_xcp_dev_register(struct amdgpu_device 
*adev,
                 return 0;

         for (i = 1; i < MAX_XCP; i++) {
+               if (!adev->xcp_mgr->xcp[i].ddev)
+                       break;
+
                 ret = drm_dev_register(adev->xcp_mgr->xcp[i].ddev, 
ent->driver_data);
                 if (ret)
                         return ret;
@@ -345,6 +353,9 @@ void amdgpu_xcp_dev_unplug(struct amdgpu_device *adev)
                 return;

         for (i = 1; i < MAX_XCP; i++) {
+               if (!adev->xcp_mgr->xcp[i].ddev)
+                       break;
+
                 p_ddev = adev->xcp_mgr->xcp[i].ddev;
                 drm_dev_unplug(p_ddev);
                 p_ddev->render->dev = adev->xcp_mgr->xcp[i].rdev;
diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_topology.c 
b/drivers/gpu/drm/amd/amdkfd/kfd_topology.c
index 3b0749390388..310df98ba46a 100644
--- a/drivers/gpu/drm/amd/amdkfd/kfd_topology.c
+++ b/drivers/gpu/drm/amd/amdkfd/kfd_topology.c
@@ -1969,8 +1969,16 @@ int kfd_topology_add_device(struct kfd_node *gpu)
         int i;
         const char *asic_name = amdgpu_asic_name[gpu->adev->asic_type];

+
         gpu_id = kfd_generate_gpu_id(gpu);
-       pr_debug("Adding new GPU (ID: 0x%x) to topology\n", gpu_id);
+       if (!gpu->xcp->ddev) {
+               dev_warn(gpu->adev->dev,
+               "Won't add GPU (ID: 0x%x) to topology since it has no 
drm node assigned.",
+               gpu_id);
+               return 0;
+       } else {
+               pr_debug("Adding new GPU (ID: 0x%x) to topology\n", 
gpu_id);
+       }

         /* Check to see if this gpu device exists in the 
topology_device_list.
          * If so, assign the gpu to that device,
--
2.34.1







