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Date:   Wed, 30 Aug 2023 10:56:55 -0700
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Subject: Re: [PATCH v8 5/8] x86/resctrl: Unwind the errors inside
 rdt_enable_ctx()
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To:     <babu.moger@amd.com>, <corbet@lwn.net>, <tglx@linutronix.de>,
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References: <20230821233048.434531-1-babu.moger@amd.com>
 <20230821233048.434531-6-babu.moger@amd.com>
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 <54236122-55d8-fd4a-1791-e6f96a61e3f0@amd.com>
From:   Reinette Chatre <reinette.chatre@intel.com>
In-Reply-To: <54236122-55d8-fd4a-1791-e6f96a61e3f0@amd.com>
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Hi Babu,

On 8/30/2023 9:38 AM, Moger, Babu wrote:
> On 8/29/23 15:10, Reinette Chatre wrote:
>> On 8/21/2023 4:30 PM, Babu Moger wrote:
>>>  static int rdt_enable_ctx(struct rdt_fs_context *ctx)
>>>  {
>>>  	int ret = 0;
>>>  
>>> -	if (ctx->enable_cdpl2)
>>> +	if (ctx->enable_cdpl2) {
>>>  		ret = resctrl_arch_set_cdp_enabled(RDT_RESOURCE_L2, true);
>>> +		if (ret)
>>> +			goto out_done;
>>> +	}
>>>  
>>> -	if (!ret && ctx->enable_cdpl3)
>>> +	if (ctx->enable_cdpl3) {
>>>  		ret = resctrl_arch_set_cdp_enabled(RDT_RESOURCE_L3, true);
>>> +		if (ret)
>>> +			goto out_cdpl2;
>>> +	}
>>>  
>>> -	if (!ret && ctx->enable_mba_mbps)
>>> +	if (ctx->enable_mba_mbps) {
>>>  		ret = set_mba_sc(true);
>>> +		if (ret)
>>> +			goto out_cdpl3;
>>
>> An error may be encountered here without CDP ever enabled or just
>> enabled for L2 or L3. I think that the error unwinding should
>> take care to not unwind an action that was not done. Considering
>> the information available I think checking either ctx->enable_...
>> or the checks used in rdt_disable_ctx() would be ok but for consistency
>> the resctrl_arch_get_cdp_enabled() checks may be most appropriate.
>>
>>> +	}
>>> +
>>> +	return 0;
>>>  
>>> +out_cdpl3:
>>
>> So here I think there should be a check. 
>> 	if (resctrl_arch_get_cdp_enabled(RDT_RESOURCE_L3))
>>
>>> +	resctrl_arch_set_cdp_enabled(RDT_RESOURCE_L3, false);
>>> +out_cdpl2:
>>
>> ... and here a check:
>> 	if (resctrl_arch_get_cdp_enabled(RDT_RESOURCE_L2))
> 
> 
> I know it does not hurt to add these checks.  But, it may be unnecessary
> considering  cdp_disable() has the check "if (r_hw->cdp_enabled)" already.
> Both are same checks. What do you think?

Yes, good point. Thank you for checking. Considering this it looks like
rdt_disable_ctx() can be simplified also by removing those CDP
enabled checks from it? Also looks like rdt_disable_ctx()-> set_mba_sc(false)
can be called unconditionally.

Reinette