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To: jarkko@kernel.org, dave.hansen@linux.intel.com, tj@kernel.org,
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Cc: zhiquan1.li@intel.com, kristen@linux.intel.com, seanjc@google.com,
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Subject: Re: [PATCH v9 09/15] x86/sgx: Charge mem_cgroup for per-cgroup
 reclamation
References: <20240205210638.157741-1-haitao.huang@linux.intel.com>
 <20240205210638.157741-10-haitao.huang@linux.intel.com>
 <8a31fce6-9ad2-4868-b6bf-15997ef18334@intel.com>
Date: Fri, 16 Feb 2024 00:07:28 -0600
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From: "Haitao Huang" <haitao.huang@linux.intel.com>
Organization: Intel
Message-ID: <op.2i70mqs3wjvjmi@hhuan26-mobl.amr.corp.intel.com>
In-Reply-To: <8a31fce6-9ad2-4868-b6bf-15997ef18334@intel.com>
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Hi Dave,

On Thu, 15 Feb 2024 17:43:18 -0600, Dave Hansen <dave.hansen@intel.com>  
wrote:

> On 2/5/24 13:06, Haitao Huang wrote:
>>  static struct mem_cgroup *sgx_encl_get_mem_cgroup(struct sgx_encl  
>> *encl)
>>  {
>> @@ -1003,14 +1001,6 @@ static struct mem_cgroup  
>> *sgx_encl_get_mem_cgroup(struct sgx_encl *encl)
>>  	struct sgx_encl_mm *encl_mm;
>>  	int idx;
>>
>> -	/*
>> -	 * If called from normal task context, return the mem_cgroup
>> -	 * of the current task's mm. The remainder of the handling is for
>> -	 * ksgxd.
>> -	 */
>> -	if (!current_is_ksgxd())
>> -		return get_mem_cgroup_from_mm(current->mm);
>
> Why is this being removed?
>
> Searching the enclave mm list is a last resort.  It's expensive and
> imprecise.
>
> get_mem_cgroup_from_mm(current->mm), on the other hand is fast and  
> precise.
>

I introduced a boolean flag to indicate caller is in kthread (ksgxd or  
cgroup workqueue), so sgx_encl_alloc_backing only calls this function if  
that flag is true, meaning search through the mm_list is needed.

But now I think a more straightforward way is to just replace  
current_is_ksgxd() with (current->flags & PF_KTHREAD).

Thanks

Haitao