On 2024-05-03 18:06, 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.kasiviswanat...@amd.com> --- 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);+ /* 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;
This doesn't catch the case that hashout was 0 before incrementing it, and was found to be unique.
Regards, Felix
+ } + } 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;
