On 5/10/2024 1:36 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
> v3: Use crc16 as suggested-by: Lijo Lazar <lijo.lazar@xxxxxxx>
> Ensure that gpu_id != 0
>
> Signed-off-by: Harish Kasiviswanathan <Harish.Kasiviswanathan@xxxxxxx>
Reviewed-by: Lijo Lazar <lijo.lazar@xxxxxxx>
Thanks,
Lijo
> ---
> drivers/gpu/drm/amd/amdkfd/kfd_topology.c | 40 +++++++++++++++++++----
> 1 file changed, 34 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_topology.c b/drivers/gpu/drm/amd/amdkfd/kfd_topology.c
> index 219dcf504f24..4954a3021f70 100644
> --- a/drivers/gpu/drm/amd/amdkfd/kfd_topology.c
> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_topology.c
> @@ -31,6 +31,7 @@
> #include <linux/log2.h>
> #include <linux/dmi.h>
> #include <linux/atomic.h>
> +#include <linux/crc16.h>
>
> #include "kfd_priv.h"
> #include "kfd_crat.h"
> @@ -1091,14 +1092,17 @@ void kfd_topology_shutdown(void)
>
> static uint32_t kfd_generate_gpu_id(struct kfd_node *gpu)
> {
> - uint32_t hashout;
> + uint32_t gpu_id;
> uint32_t buf[8];
> uint64_t local_mem_size;
> - int i;
> + struct kfd_topology_device *dev;
> + bool is_unique;
> + uint8_t *crc_buf;
>
> if (!gpu)
> return 0;
>
> + crc_buf = (uint8_t*)&buf;
> local_mem_size = gpu->local_mem_info.local_mem_size_private +
> gpu->local_mem_info.local_mem_size_public;
> buf[0] = gpu->adev->pdev->devfn;
> @@ -1111,10 +1115,34 @@ static uint32_t kfd_generate_gpu_id(struct kfd_node *gpu)
> buf[6] = upper_32_bits(local_mem_size);
> buf[7] = (ffs(gpu->xcc_mask) - 1) | (NUM_XCC(gpu->xcc_mask) << 16);
>
> - for (i = 0, hashout = 0; i < 8; i++)
> - hashout ^= hash_32(buf[i], KFD_GPU_ID_HASH_WIDTH);
> + gpu_id = crc16(0, crc_buf, sizeof(buf)) &
> + ((1 << KFD_GPU_ID_HASH_WIDTH) - 1);
>
> - return hashout;
> + /* There is a very small possibility when generating a
> + * 16 (KFD_GPU_ID_HASH_WIDTH) bit value from 8 word buffer
> + * that the value could be 0 or non-unique. So, check if
> + * it is unique and non-zero. If not unique increment till
> + * unique one is found. In case of overflow, restart from 1
> + */
> +
> + down_read(&topology_lock);
> + do {
> + is_unique = true;
> + if (!gpu_id)
> + gpu_id = 1;
> + list_for_each_entry(dev, &topology_device_list, list) {
> + if (dev->gpu && dev->gpu_id == gpu_id) {
> + is_unique = false;
> + break;
> + }
> + }
> + if (unlikely(!is_unique))
> + gpu_id = (gpu_id + 1) &
> + ((1 << KFD_GPU_ID_HASH_WIDTH) - 1);
> + } while (!is_unique);
> + up_read(&topology_lock);
> +
> + return gpu_id;
> }
> /* kfd_assign_gpu - Attach @gpu to the correct kfd topology device. If
> * the GPU device is not already present in the topology device
> @@ -1945,7 +1973,6 @@ 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.");
> @@ -1968,6 +1995,7 @@ 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;
>
