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.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);
+ /* 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;
