linux-kernel - Re: [PATCH v7 09/15] x86/sgx: Charge mem

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Date: Fri, 02 Feb 2024 18:39:23 -0600
From: "Haitao Huang" <haitao.huang@...ux.intel.com>
To: jarkko@...nel.org, dave.hansen@...ux.intel.com, tj@...nel.org,
 mkoutny@...e.com, linux-kernel@...r.kernel.org, linux-sgx@...r.kernel.org,
 x86@...nel.org, cgroups@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
 bp@...en8.de, hpa@...or.com, sohil.mehta@...el.com, "Tim Chen"
 <tim.c.chen@...ux.intel.com>
Cc: zhiquan1.li@...el.com, kristen@...ux.intel.com, seanjc@...gle.com,
 zhanb@...rosoft.com, anakrish@...rosoft.com, mikko.ylinen@...ux.intel.com,
 yangjie@...rosoft.com
Subject: Re: [PATCH v7 09/15] x86/sgx: Charge mem_cgroup for per-cgroup
 reclamation

Hi Tim,
On Fri, 02 Feb 2024 17:45:05 -0600, Tim Chen <tim.c.chen@...ux.intel.com>  
wrote:

> On Mon, 2024-01-22 at 09:20 -0800, Haitao Huang wrote:
>>
>> @@ -1047,29 +1037,38 @@ static struct mem_cgroup  
>> *sgx_encl_get_mem_cgroup(struct sgx_encl *encl)
>>   * @encl:	an enclave pointer
>>   * @page_index:	enclave page index
>>   * @backing:	data for accessing backing storage for the page
>> + * @indirect:	in ksgxd or EPC cgroup work queue context
>> + *
>> + * Create a backing page for loading data back into an EPC page with  
>> ELDU. This function takes
>> + * a reference on a new backing page which must be dropped with a  
>> corresponding call to
>> + * sgx_encl_put_backing().
>>   *
>> - * When called from ksgxd, sets the active memcg from one of the
>> - * mms in the enclave's mm_list prior to any backing page allocation,
>> - * in order to ensure that shmem page allocations are charged to the
>> - * enclave.  Create a backing page for loading data back into an EPC  
>> page with
>> - * ELDU.  This function takes a reference on a new backing page which
>> - * must be dropped with a corresponding call to sgx_encl_put_backing().
>> + * When @indirect is true, sets the active memcg from one of the mms  
>> in the enclave's mm_list
>> + * prior to any backing page allocation, in order to ensure that shmem  
>> page allocations are
>> + * charged to the enclave.
>>   *
>>   * Return:
>>   *   0 on success,
>>   *   -errno otherwise.
>>   */
>>  int sgx_encl_alloc_backing(struct sgx_encl *encl, unsigned long  
>> page_index,
>> -			   struct sgx_backing *backing)
>> +			   struct sgx_backing *backing, bool indirect)
>>  {
>> -	struct mem_cgroup *encl_memcg = sgx_encl_get_mem_cgroup(encl);
>> -	struct mem_cgroup *memcg = set_active_memcg(encl_memcg);
>> +	struct mem_cgroup *encl_memcg;
>> +	struct mem_cgroup *memcg;
>>  	int ret;
>>
>> +	if (indirect) {
>> +		encl_memcg = sgx_encl_get_mem_cgroup(encl);
>> +		memcg = set_active_memcg(encl_memcg);
>> +	}
>> +
>>  	ret = __sgx_encl_get_backing(encl, page_index, backing);
>>
>> -	set_active_memcg(memcg);
>> -	mem_cgroup_put(encl_memcg);
>> +	if (indirect) {
>> +		set_active_memcg(memcg);
>> +		mem_cgroup_put(encl_memcg);
>> +	}
>>
>
>
> You can reduce the number of if statements to make the logic
> simpler.  Something like
>
> 	if (!indirect)
> 		return __sgx_encl_get_backing(encl, page_index, backing);
>
> 	encl_memcg = sgx_encl_get_mem_cgroup(encl);
> 	memcg = set_active_memcg(encl_memcg);
> 	ret = __sgx_encl_get_backing(encl, page_index, backing);
> 	set_active_memcg(memcg);
> 	mem_cgroup_put(encl_memcg);
>
>>  	return ret;
>
> Tim
>

Yes, will do.
Thanks
Haitao