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To: =?iso-8859-15?Q?Michal_Koutn=FD?= <mkoutny@suse.com>
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Subject: Re: Re: [PATCH v10 12/14] x86/sgx: Turn on per-cgroup EPC reclamation
References: <20240328002229.30264-1-haitao.huang@linux.intel.com>
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Date: Tue, 09 Apr 2024 10:34:06 -0500
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From: "Haitao Huang" <haitao.huang@linux.intel.com>
Organization: Intel
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On Tue, 09 Apr 2024 04:03:22 -0500, Michal Koutn=FD <mkoutny@suse.com> w=
rote:

> On Mon, Apr 08, 2024 at 11:23:21PM -0500, Haitao Huang  =

> <haitao.huang@linux.intel.com> wrote:
>> It's always non-NULL based on testing.
>>
>> It's hard for me to say definitely by reading the code. But IIUC
>> cgroup_disable command-line only blocks operations in /sys/fs/cgroup =
so  =

>> user
>> space can't set up controllers and config limits, etc., for the  =

>> diasabled
>> ones. Each task->cgroups would still have a non-NULL pointer to the  =

>> static
>> root object for each cgroup that is enabled by KConfig, so
>> get_current_misc_cg() thus  sgx_get_current_cg() should not return NU=
LL
>> regardless 'cgroup_disable=3Dmisc'.
>>
>> Maybe @Michal or @tj can confirm?
>
> The current implementation creates root css object (see cgroup_init(),=

> cgroup_ssid_enabled() check is after cgroup_init_subsys()).
> I.e. it will look like all tasks are members of root cgroup wrt given
> controller permanently and controller attribute files won't exist.
>
> (It is up to the controller implementation to do further optimization
> based on the boot-time disablement (e.g. see uses of
> mem_cgroup_disabled()). Not sure if this is useful for misc controller=
)
>
> As for the WARN_ON(1), taking example from memcg -- NULL is best
> synonymous with root. It's a judgement call which of the values to sto=
re
> and when to intepret it.
>
> HTH,
> Michal
Thanks for the info.

The way I see it, misc does not have special handling like memcg so ever=
y  =

task at least belong to the root(default) group even if it's disabled by=
  =

command line parameter. So we would not get NULL from  =

get_current_misc_cg(). I think I'll keep the WARN_ON_ONCE for now as a  =

reminder in case misc do have custom support for disabling in future.

Thanks
Haitao