linux-kernel - Re: [PATCH v8 5/8] x86/resctrl: Unwind the errors inside rdt_enable

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Message-ID: <343d12e8-9934-9194-cadd-7d133567396c@intel.com>
Date:   Tue, 29 Aug 2023 13:10:23 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     Babu Moger <babu.moger@....com>, <corbet@....net>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>
CC:     <fenghua.yu@...el.com>, <dave.hansen@...ux.intel.com>,
        <x86@...nel.org>, <hpa@...or.com>, <paulmck@...nel.org>,
        <akpm@...ux-foundation.org>, <quic_neeraju@...cinc.com>,
        <rdunlap@...radead.org>, <damien.lemoal@...nsource.wdc.com>,
        <songmuchun@...edance.com>, <peterz@...radead.org>,
        <jpoimboe@...nel.org>, <pbonzini@...hat.com>,
        <chang.seok.bae@...el.com>, <pawan.kumar.gupta@...ux.intel.com>,
        <jmattson@...gle.com>, <daniel.sneddon@...ux.intel.com>,
        <sandipan.das@....com>, <tony.luck@...el.com>,
        <james.morse@....com>, <linux-doc@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <bagasdotme@...il.com>,
        <eranian@...gle.com>, <christophe.leroy@...roup.eu>,
        <jarkko@...nel.org>, <adrian.hunter@...el.com>,
        <quic_jiles@...cinc.com>, <peternewman@...gle.com>
Subject: Re: [PATCH v8 5/8] x86/resctrl: Unwind the errors inside
 rdt_enable_ctx()

Hi Babu,

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))

> +	resctrl_arch_set_cdp_enabled(RDT_RESOURCE_L2, false);
> +out_done:
>  	return ret;
>  }
>  

Reinette