On 10/18/2025 7:16 AM, Felix Kuehling wrote:
> On 2025-10-17 04:42, Zhu Lingshan wrote:
>> This commit introduces a new id field for
>> struct kfd process, which helps identify
>> a kfd process among multiple contexts that
>> all belong to a single user space program.
>>
>> The sysfs entry of a secondary kfd process
>> is placed under the sysfs entry folder of
>> its primary kfd process.
>>
>> The naming format of the sysfs entry of a secondary
>> kfd process is "context_%u" where %u is the process id.
>>
>> Signed-off-by: Zhu Lingshan <[email protected]>
>> ---
>> drivers/gpu/drm/amd/amdkfd/kfd_priv.h | 6 ++
>> drivers/gpu/drm/amd/amdkfd/kfd_process.c | 78 +++++++++++++++++++++++-
>> 2 files changed, 81 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
>> b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
>> index 919510f18249..9de658119cd9 100644
>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_priv.h
>> @@ -1021,10 +1021,16 @@ struct kfd_process {
>> /*kfd context id */
>> u16 context_id;
>> +
>> + /* The primary kfd_process allocating IDs for its secondary
>> kfd_process, 0 for primary kfd_process */
>> + struct ida id_table;
>> +
>> };
>> #define KFD_PROCESS_TABLE_SIZE 8 /* bits: 256 entries */
>> #define KFD_CONTEXT_ID_PRIMARY 0xFFFF
>> +#define KFD_CONTEXT_ID_MIN 0
>> +#define KFD_CONTEXT_ID_WIDTH 16
>> extern DECLARE_HASHTABLE(kfd_processes_table,
>> KFD_PROCESS_TABLE_SIZE);
>> extern struct srcu_struct kfd_processes_srcu;
>> diff --git a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
>> b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
>> index 995d27be06e3..157145c94314 100644
>> --- a/drivers/gpu/drm/amd/amdkfd/kfd_process.c
>> +++ b/drivers/gpu/drm/amd/amdkfd/kfd_process.c
>> @@ -827,6 +827,7 @@ static void
>> kfd_process_device_destroy_ib_mem(struct kfd_process_device *pdd)
>> int kfd_create_process_sysfs(struct kfd_process *process)
>> {
>> + struct kfd_process *primary_process;
>> int ret;
>> if (process->kobj) {
>> @@ -839,9 +840,22 @@ int kfd_create_process_sysfs(struct kfd_process
>> *process)
>> pr_warn("Creating procfs kobject failed");
>> return -ENOMEM;
>> }
>> - ret = kobject_init_and_add(process->kobj, &procfs_type,
>> - procfs.kobj, "%d",
>> - (int)process->lead_thread->pid);
>> +
>> + if (process->context_id == KFD_CONTEXT_ID_PRIMARY)
>> + ret = kobject_init_and_add(process->kobj, &procfs_type,
>> + procfs.kobj, "%d",
>> + (int)process->lead_thread->pid);
>> + else {
>> + primary_process =
>> kfd_lookup_process_by_mm(process->lead_thread->mm);
>> + if (!primary_process)
>> + return -ESRCH;
>> +
>> + ret = kobject_init_and_add(process->kobj, &procfs_type,
>> + primary_process->kobj, "context_%u",
>> + process->context_id);
>> + kfd_unref_process(primary_process);
>> + }
>> +
>> if (ret) {
>> pr_warn("Creating procfs pid directory failed");
>> kobject_put(process->kobj);
>> @@ -863,6 +877,50 @@ int kfd_create_process_sysfs(struct kfd_process
>> *process)
>> return 0;
>> }
>> +static int kfd_process_alloc_id(struct kfd_process *process)
>> +{
>> + int ret;
>> + struct kfd_process *primary_process;
>> +
>> + /* already assign 0xFFFF when create */
>> + if (process->context_id == KFD_CONTEXT_ID_PRIMARY)
>> + return 0;
>> +
>> + primary_process =
>> kfd_lookup_process_by_mm(process->lead_thread->mm);
>> + if (!primary_process)
>> + return -ESRCH;
>> +
>> + /* id range: KFD_CONTEXT_ID_MIN to 0xFFFE */
>> + ret = ida_alloc_range(&primary_process->id_table,
>> KFD_CONTEXT_ID_MIN,
>> + (1 << KFD_CONTEXT_ID_WIDTH) - 2, GFP_KERNEL);
>
> This would be safer and more obvious if you just set the upper limit
> as KFD_CONTEXT_ID_PRIMARY - 1. Then you don't need
> KFD_CONTEXT_ID_WIDTH at all.
will fix in V6, thanks!
>
> Regards,
> Felix
>
>
>> + if (ret < 0)
>> + goto out;
>> +
>> + process->context_id = ret;
>> + ret = 0;
>> +
>> +out:
>> + kfd_unref_process(primary_process);
>> +
>> + return ret;
>> +}
>> +
>> +static void kfd_process_free_id(struct kfd_process *process)
>> +{
>> + struct kfd_process *primary_process;
>> +
>> + if (process->context_id != KFD_CONTEXT_ID_PRIMARY)
>> + return;
>> +
>> + primary_process =
>> kfd_lookup_process_by_mm(process->lead_thread->mm);
>> + if (!primary_process)
>> + return;
>> +
>> + ida_free(&primary_process->id_table, process->context_id);
>> +
>> + kfd_unref_process(primary_process);
>> +}
>> +
>> struct kfd_process *kfd_create_process(struct task_struct *thread)
>> {
>> struct kfd_process *process;
>> @@ -1195,6 +1253,11 @@ static void kfd_process_wq_release(struct
>> work_struct *work)
>> if (ef)
>> dma_fence_signal(ef);
>> + if (p->context_id != KFD_CONTEXT_ID_PRIMARY)
>> + kfd_process_free_id(p);
>> + else
>> + ida_destroy(&p->id_table);
>> +
>> kfd_process_remove_sysfs(p);
>> kfd_debugfs_remove_process(p);
>> @@ -1601,6 +1664,13 @@ static struct kfd_process
>> *create_process(const struct task_struct *thread, bool
>> goto err_register_notifier;
>> }
>> BUG_ON(mn != &process->mmu_notifier);
>> + ida_init(&process->id_table);
>> + }
>> +
>> + err = kfd_process_alloc_id(process);
>> + if (err) {
>> + pr_err("Creating kfd process: failed to alloc an id\n");
>> + goto err_alloc_id;
>> }
>> kfd_unref_process(process);
>> @@ -1610,6 +1680,8 @@ static struct kfd_process *create_process(const
>> struct task_struct *thread, bool
>> return process;
>> +err_alloc_id:
>> + kfd_process_free_id(process);
>> err_register_notifier:
>> hash_del_rcu(&process->kfd_processes);
>> svm_range_list_fini(process);
