linux-kernel - Re: [PATCH v6 19/22] x86/resctrl: Introduce the interface to switch between monitor modes

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Message-ID: <8b23eade-9015-4d40-b9f9-f7cf5a9d08c6@amd.com>
Date: Wed, 21 Aug 2024 13:08:38 -0500
From: "Moger, Babu" <babu.moger@....com>
To: Reinette Chatre <reinette.chatre@...el.com>, corbet@....net,
 fenghua.yu@...el.com, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
 dave.hansen@...ux.intel.com
Cc: x86@...nel.org, hpa@...or.com, paulmck@...nel.org, rdunlap@...radead.org,
 tj@...nel.org, peterz@...radead.org, yanjiewtw@...il.com,
 kim.phillips@....com, lukas.bulwahn@...il.com, seanjc@...gle.com,
 jmattson@...gle.com, leitao@...ian.org, jpoimboe@...nel.org,
 rick.p.edgecombe@...el.com, kirill.shutemov@...ux.intel.com,
 jithu.joseph@...el.com, kai.huang@...el.com, kan.liang@...ux.intel.com,
 daniel.sneddon@...ux.intel.com, pbonzini@...hat.com, sandipan.das@....com,
 ilpo.jarvinen@...ux.intel.com, peternewman@...gle.com,
 maciej.wieczor-retman@...el.com, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org, eranian@...gle.com, james.morse@....com
Subject: Re: [PATCH v6 19/22] x86/resctrl: Introduce the interface to switch
 between monitor modes

Hi Reinette,

On 8/16/24 16:42, Reinette Chatre wrote:
> Hi Babu,
> 
> On 8/6/24 3:00 PM, Babu Moger wrote:
>> +static ssize_t rdtgroup_mbm_mode_write(struct kernfs_open_file *of,
>> +                       char *buf, size_t nbytes,
>> +                       loff_t off)
>> +{
>> +    int mbm_cntr_assign = resctrl_arch_get_abmc_enabled();
> 
> This needs to be protected by the mutex.

Agree.. Will do.

> 
>> +    struct rdt_resource *r = of->kn->parent->priv;
>> +    int ret = 0;
>> +
>> +    /* Valid input requires a trailing newline */
>> +    if (nbytes == 0 || buf[nbytes - 1] != '\n')
>> +        return -EINVAL;
>> +
>> +    buf[nbytes - 1] = '\0';
>> +
>> +    cpus_read_lock();
>> +    mutex_lock(&rdtgroup_mutex);
>> +
>> +    rdt_last_cmd_clear();
>> +
>> +    if (!strcmp(buf, "legacy")) {
>> +        if (mbm_cntr_assign)
>> +            resctrl_arch_mbm_cntr_assign_disable();
>> +    } else if (!strcmp(buf, "mbm_cntr_assign")) {
>> +        if (!mbm_cntr_assign) {
>> +            rdtgroup_mbm_cntr_reset(r);
>> +            ret = resctrl_arch_mbm_cntr_assign_enable();
>> +        }
>> +    } else {
>> +        ret = -EINVAL;
>> +    }
>> +
>> +    mutex_unlock(&rdtgroup_mutex);
>> +    cpus_read_unlock();
>> +
>> +    return ret ?: nbytes;
>> +}
>> +
> 
> Reinette
> 

-- 
Thanks
Babu Moger