linux-kernel - Re: [PATCH v4 15/21] x86/resctrl: Abstract __rmid

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Date:   Tue, 17 May 2022 14:23:24 -0700
From:   Reinette Chatre <reinette.chatre@...el.com>
To:     James Morse <james.morse@....com>, <x86@...nel.org>,
        <linux-kernel@...r.kernel.org>
CC:     Fenghua Yu <fenghua.yu@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        Babu Moger <Babu.Moger@....com>,
        <shameerali.kolothum.thodi@...wei.com>,
        D Scott Phillips OS <scott@...amperecomputing.com>,
        <lcherian@...vell.com>, <bobo.shaobowang@...wei.com>,
        <tan.shaopeng@...itsu.com>, Jamie Iles <quic_jiles@...cinc.com>,
        Cristian Marussi <cristian.marussi@....com>,
        "Xin Hao" <xhao@...ux.alibaba.com>, <xingxin.hx@...nanolis.org>,
        <baolin.wang@...ux.alibaba.com>
Subject: Re: [PATCH v4 15/21] x86/resctrl: Abstract __rmid_read()

Hi James,

On 4/12/2022 5:44 AM, James Morse wrote:

> @@ -180,14 +180,24 @@ static u64 __rmid_read(u32 rmid, enum resctrl_event_id eventid)
>  	 * are error bits.
>  	 */
>  	wrmsr(MSR_IA32_QM_EVTSEL, eventid, rmid);
> -	rdmsrl(MSR_IA32_QM_CTR, val);
> +	rdmsrl(MSR_IA32_QM_CTR, msr_val);
>  
> -	return val;
> +	if (msr_val & RMID_VAL_ERROR)
> +		return -EIO;
> +	if (msr_val & RMID_VAL_UNAVAIL)
> +		return -EINVAL;
> +
> +	*val = msr_val;
> +
> +	return 0;
>  }
>  

In above EIO is used to represent RMID_VAL_ERROR ...

> @@ -343,7 +355,7 @@ static u64 __mon_event_count(u32 rmid, struct rmid_read *rr)
>  		 * Code would never reach here because an invalid
>  		 * event id would fail the __rmid_read.
>  		 */
> -		return RMID_VAL_ERROR;
> +		return -EINVAL;
>  	}
>  
>  	if (rr->first) {

I understand it can be seen as a symbolic change but could
RMID_VAL_ERROR consistently be associated with the same error?

Reinette