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

[Lazar, Lijo]

[AMD Official Use Only - General]

A dynamic partition switch could happen later.  The switch could still be successful in terms of hardware, 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.

Also, a kfd node is not expected to have a valid xcp pointer on devices without partition. This access could break then gpu->xcp->ddev.

Thanks,
Lijo
________________________________
From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> on behalf of James Zhu <James.Zhu at amd.com>
Sent: Saturday, August 12, 2023 2:36:27 AM
To: amd-gfx at lists.freedesktop.org <amd-gfx at lists.freedesktop.org>
Cc: Lin, Amber <Amber.Lin at amd.com>; Zhu, James <James.Zhu at amd.com>; Kasiviswanathan, Harish <Harish.Kasiviswanathan at amd.com>; Koenig, Christian <Christian.Koenig at amd.com>
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@intel.com/T/
libdrm:
https://gitlab.freedesktop.org/mesa/drm/-/merge_requests/305

Signed-off-by: James Zhu <James.Zhu at amd.com>
Acked-by: Christian König <christian.koenig at amd.com>

-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

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