linux-kernel - Re: [PATCH v6 20/22] x86/resctrl: Enable AMD ABMC feature by default when supported

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Message-ID: <df0c32ef-a694-4e5a-9d93-54ae2b93e452@arm.com>
Date: Fri, 16 Aug 2024 17:32:10 +0100
From: James Morse <james.morse@....com>
To: Babu Moger <babu.moger@....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,
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 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,
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 reinette.chatre@...el.com, tglx@...utronix.de, dave.hansen@...ux.intel.com
Subject: Re: [PATCH v6 20/22] x86/resctrl: Enable AMD ABMC feature by default
 when supported

Hi Babu,

On 06/08/2024 23:00, Babu Moger wrote:
> Enable ABMC by default when supported during the boot up.
> 
> Users will not see any difference in the behavior when resctrl is
> mounted. With automatic assignment everything will work as running
> in the legacy monitor mode.

> diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
> index 6fb0cfdb5529..a7980f84c487 100644
> --- a/arch/x86/kernel/cpu/resctrl/core.c
> +++ b/arch/x86/kernel/cpu/resctrl/core.c
> @@ -599,6 +599,7 @@ static void domain_add_cpu_mon(int cpu, struct rdt_resource *r)
>  		d = container_of(hdr, struct rdt_mon_domain, hdr);
>  
>  		cpumask_set_cpu(cpu, &d->hdr.cpu_mask);
> +		resctrl_arch_mbm_cntr_assign_configure();
>  		return;
>  	}
>  
> @@ -620,6 +621,7 @@ static void domain_add_cpu_mon(int cpu, struct rdt_resource *r)
>  	arch_mon_domain_online(r, d);
>  
>  	resctrl_mbm_evt_config_init(hw_dom);
> +	resctrl_arch_mbm_cntr_assign_configure();
>  
>  	if (arch_domain_mbm_alloc(r->mon.num_rmid, hw_dom)) {
>  		mon_domain_free(hw_dom);

> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 66febff2a3d3..d15fd1bde5f4 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -2756,6 +2756,23 @@ void resctrl_arch_mbm_cntr_assign_disable(void)
>  	}
>  }
>  
> +void resctrl_arch_mbm_cntr_assign_configure(void)
> +{
> +	struct rdt_resource *r = &rdt_resources_all[RDT_RESOURCE_L3].r_resctrl;
> +	struct rdt_hw_resource *hw_res = resctrl_to_arch_res(r);
> +	bool enable = true;
> +
> +	mutex_lock(&rdtgroup_mutex);

As before - this lock isn't available to the architecture code after the filesystem code
moves to /fs/. To prevent concurrent calls to resctrl_abmc_set_one_amd() I think you need
your own mutex.


> +	if (r->mon.mbm_cntr_assignable) {
> +		if (!hw_res->mbm_cntr_assign_enabled)
> +			hw_res->mbm_cntr_assign_enabled = true;
> +		resctrl_abmc_set_one_amd(&enable);
> +	}
> +
> +	mutex_unlock(&rdtgroup_mutex);
> +}

Neither of this functions callers are in filesystem code, could you drop the 'arch' from
the name - it isn't part of the fs/arch interface.


Thanks,

James