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Message-ID: <b48d2489-a5af-d9af-08e6-cbc2d5d8194f@intel.com>
Date: Wed, 30 Aug 2023 10:56:55 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: <babu.moger@....com>, <corbet@....net>, <tglx@...utronix.de>,
<mingo@...hat.com>, <bp@...en8.de>
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Subject: Re: [PATCH v8 5/8] x86/resctrl: Unwind the errors inside
rdt_enable_ctx()
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
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