Re: [PATCH v8 5/8] x86/resctrl: Unwind the errors inside rdt_enable_ctx()

["Moger, Babu" <babu.moger@amd.com>]

Hi Reinette,

On 8/30/23 12:56, Reinette Chatre wrote:
> 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.

Yes. We can do that.
-- 
Thanks
Babu Moger