linux-kernel - Re: [PATCH v3 10/19] x86/resctrl: Allow resctrl_arch_rmid

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Message-ID: <db59f6df-feb0-280d-88bd-6bbf1b6e7a1e@intel.com>
Date:   Fri, 31 Mar 2023 16:26:11 -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>,
        <carl@...amperecomputing.com>, <lcherian@...vell.com>,
        <bobo.shaobowang@...wei.com>, <tan.shaopeng@...itsu.com>,
        <xingxin.hx@...nanolis.org>, <baolin.wang@...ux.alibaba.com>,
        Jamie Iles <quic_jiles@...cinc.com>,
        Xin Hao <xhao@...ux.alibaba.com>, <peternewman@...gle.com>
Subject: Re: [PATCH v3 10/19] x86/resctrl: Allow resctrl_arch_rmid_read() to
 sleep

Hi James,

On 3/20/2023 10:26 AM, James Morse wrote:

...

>  int resctrl_arch_rmid_read(struct rdt_resource *r, struct rdt_domain *d,
>  			   u32 closid, u32 rmid, enum resctrl_event_id eventid,
>  			   u64 *val)
>  {
>  	struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
>  	struct rdt_hw_domain *hw_dom = resctrl_to_arch_dom(d);
> +	struct __rmid_read_arg arg;
>  	struct arch_mbm_state *am;
>  	u64 msr_val, chunks;
> -	int ret;
> +	int err;
>  
> -	if (!cpumask_test_cpu(smp_processor_id(), &d->cpu_mask))
> -		return -EINVAL;
> +	arg.rmid = rmid;
> +	arg.eventid = eventid;
>  
> -	ret = __rmid_read(rmid, eventid, &msr_val);
> -	if (ret)
> -		return ret;
> +	err = smp_call_function_any(&d->cpu_mask, smp_call_rmid_read, &arg, true);
> +	if (err)
> +		return err;

This seems to break the assumption of expected return values. __mon_event_count()
does: 
	rr->err = resctrl_arch_rmid_read()

and later rdtgroup_mondata_show() only expects -EIO or -EINVAL as errors, with
default of success.


> +	if (arg.err)
> +		return arg.err;
> +	msr_val = arg.msr_val;
>  


Reinette