[Question mpam mpam/snapshot+extras/v6.18-rc1] Question with Configuring iommu_group in 'task'

[Zeng Heng]

On 2026/4/15 20:42, Ben Horgan wrote:
> Hi Zeng,
> 
> On 4/15/26 02:27, Zeng Heng wrote:
>> Hi Ben,
>>
>> On 2026/4/13 23:02, Ben Horgan wrote:
>>> Hi Qinxin,
>>>
>>> On 4/3/26 03:44, Qinxin Xia wrote:
>>>>
>>>>
>>>> On 2026/3/27 18:47:49, Ben Horgan <ben.horgan at arm.com> wrote:
>>>>> Hi Qinxin,
>>>>>
>>>>> On 3/27/26 10:21, Qinxin Xia wrote:
>>>>>>
>>>>>> Hello everyone!
>>>>>>
>>>>>> In earlier versions, mpam supports the configuration of iommu_groups.
>>>>>>
>>>>>>     823 static ssize_t rdtgroup_tasks_write(struct kernfs_open_file *of,
>>>>>>     824                                     char *buf, size_t nbytes,
>>>>>> loff_t off)
>>>>>>     825 {
>>>>>>     826         struct rdtgroup *rdtgrp;
>>>>>>     827         int iommu_group_id;
>>>>>>     828         bool is_iommu;
>>>>>>     829         char *pid_str;
>>>>>>     830         int ret = 0;
>>>>>>     831         pid_t pid;
>>>>>>     832
>>>>>>     833         rdtgrp = rdtgroup_kn_lock_live(of->kn);
>>>>>>     834         if (!rdtgrp) {
>>>>>>     835                 rdtgroup_kn_unlock(of->kn);
>>>>>>     836                 return -ENOENT;
>>>>>>     837         }
>>>>>>     838         rdt_last_cmd_clear();
>>>>>>     839
>>>>>>     840         if (rdtgrp->mode == RDT_MODE_PSEUDO_LOCKED ||
>>>>>>     841             rdtgrp->mode == RDT_MODE_PSEUDO_LOCKSETUP) {
>>>>>>     842                 ret = -EINVAL;
>>>>>>     843                 rdt_last_cmd_puts("Pseudo-locking in progress\n");
>>>>>>     844                 goto unlock;
>>>>>>     845         }
>>>>>>     846
>>>>>>     847         while (buf && buf[0] != '\0' && buf[0] != '\n') {
>>>>>>     848                 pid_str = strim(strsep(&buf, ","));
>>>>>>     849
>>>>>>     850                 is_iommu = string_is_iommu_group(pid_str, &iommu_group_id);
>>>>>>
>>>>>> What puzzles me is why we would put it under 'task'—this seems a little
>>>>>>     strange to users.It seems they are not related.Why don't we add a new
>>>>>> interface like 'iommu'?
>>>>>
>>>>> I think it is likely that this interface would change if upstream support is added.
>>>>>
>>>>
>>>> I have done some work in this direction before, and I will release an
>>>> RFC later for further discussion.:-)
>>>
>>> Looking forward to seeing it.
>>>
>>> Ben
>>>
>>
>> Following the current SMMU approach, I've submitted several bugfix
>> patches for the MPAM driver, but haven't received any review feedback
>> yet.
>>
>> To avoid these being overlooked, I'd like to kindly remind to take a
>> look:
>> v2: https://lore.kernel.org/all/20260414032610.1523958-1-zengheng4@huawei.com/
>> v1: https://lore.kernel.org/all/20251107063300.1580046-1-zengheng4@huawei.com/
>>
>> Additionally, I'd like to check on the status of this branch — is it
>> still actively maintained? It would be helpful to understand the future
>> plans for MPAM development.
> 
> The MPAM snapshot and extras branches are no longer maintained. Work on these has stopped so that we can focus on
> upstream. Apologies for not making this clear earlier.
> 


Ack. If the extras branch scheme mentioned above is rebased onto
upstream, these bugfix patches would remain applicable and worth
reviewing.


Best regards,
Zeng Heng