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

[James Zhu]

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
> 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
>
> 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
>
> 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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