On 5/4/2024 3:36 AM, Harish Kasiviswanathan wrote:
> gpu_id needs to be unique for user space to identify GPUs via KFD
> interface. In the current implementation there is a very small
> probability of having non unique gpu_ids.
>
> v2: Add check to confirm if gpu_id is unique. If not unique, find one
> Changed commit header to reflect the above
>
> Signed-off-by: Harish Kasiviswanathan <Harish.Kasiviswanathan@xxxxxxx>
> ---
> drivers/gpu/drm/amd/amdkfd/kfd_topology.c | 26 ++++++++++++++++++++++-
> 1 file changed, 25 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_topology.c b/drivers/gpu/drm/amd/amdkfd/kfd_topology.c
> index b93913934b03..01d4c2e10c6d 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_topology.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_topology.c
> @@ -1095,6 +1095,8 @@ static uint32_t kfd_generate_gpu_id(struct kfd_node *gpu)
> uint32_t hashout;
> uint32_t buf[8];
> uint64_t local_mem_size;
> + struct kfd_topology_device *dev;
> + bool is_unique;
> int i;
>
> if (!gpu)
> @@ -1115,6 +1117,28 @@ static uint32_t kfd_generate_gpu_id(struct kfd_node *gpu)
> for (i = 0, hashout = 0; i < 8; i++)
> hashout ^= hash_32(buf[i], KFD_GPU_ID_HASH_WIDTH);
Instead of this, suggest to replace this with crc16(). That has a better
chance to avoid collision as it takes into account the whole contents of
the buffer. It may work better than combining hashes with XOR.
Thanks,
Lijo
>
> + /* hash generated could be non-unique. Check if it is unique.
> + * If not unique increment till unique one is found. In case
> + * of overflow, restart from 1
> + */
> + down_read(&topology_lock);
> + do {
> + is_unique = true;
> + list_for_each_entry(dev, &topology_device_list, list) {
> + if (dev->gpu && dev->gpu_id == hashout) {
> + is_unique = false;
> + break;
> + }
> + }
> + if (unlikely(!is_unique)) {
> + hashout = (hashout + 1) &
> + ((1 << KFD_GPU_ID_HASH_WIDTH) - 1);
> + if (!hashout)
> + hashout = 1;
> + }
> + } while (!is_unique);
> + up_read(&topology_lock);
> +
> return hashout;
> }
> /* kfd_assign_gpu - Attach @gpu to the correct kfd topology device. If
> @@ -1946,7 +1970,6 @@ int kfd_topology_add_device(struct kfd_node *gpu)
> struct amdgpu_gfx_config *gfx_info = &gpu->adev->gfx.config;
> struct amdgpu_cu_info *cu_info = &gpu->adev->gfx.cu_info;
>
> - gpu_id = kfd_generate_gpu_id(gpu);
> if (gpu->xcp && !gpu->xcp->ddev) {
> dev_warn(gpu->adev->dev,
> "Won't add GPU to topology since it has no drm node assigned.");
> @@ -1969,6 +1992,7 @@ int kfd_topology_add_device(struct kfd_node *gpu)
> if (res)
> return res;
>
> + gpu_id = kfd_generate_gpu_id(gpu);
> dev->gpu_id = gpu_id;
> gpu->id = gpu_id;
>
