linux-kernel - Re: [PATCH v11 06/23] x86/resctrl: Add support to enable/disable AMD ABMC feature

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Message-ID: <e524c376-9ef8-488e-8053-b49ccafd306d@intel.com>
Date: Fri, 21 Feb 2025 10:25:25 -0800
From: Reinette Chatre <reinette.chatre@...el.com>
To: James Morse <james.morse@....com>, Babu Moger <babu.moger@....com>,
	<corbet@....net>, <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
	<dave.hansen@...ux.intel.com>, <tony.luck@...el.com>,
	<peternewman@...gle.com>
CC: <fenghua.yu@...el.com>, <x86@...nel.org>, <hpa@...or.com>,
	<paulmck@...nel.org>, <akpm@...ux-foundation.org>, <thuth@...hat.com>,
	<rostedt@...dmis.org>, <xiongwei.song@...driver.com>,
	<pawan.kumar.gupta@...ux.intel.com>, <daniel.sneddon@...ux.intel.com>,
	<jpoimboe@...nel.org>, <perry.yuan@....com>, <sandipan.das@....com>,
	<kai.huang@...el.com>, <xiaoyao.li@...el.com>, <seanjc@...gle.com>,
	<xin3.li@...el.com>, <andrew.cooper3@...rix.com>, <ebiggers@...gle.com>,
	<mario.limonciello@....com>, <tan.shaopeng@...itsu.com>,
	<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<maciej.wieczor-retman@...el.com>, <eranian@...gle.com>
Subject: Re: [PATCH v11 06/23] x86/resctrl: Add support to enable/disable AMD
 ABMC feature

Hi James,

On 2/21/25 10:05 AM, James Morse wrote:
> Hi Babu,
> 
> On 22/01/2025 20:20, Babu Moger wrote:
>> Add the functionality to enable/disable AMD ABMC feature.
>>
>> AMD ABMC feature is enabled by setting enabled bit(0) in MSR
>> L3_QOS_EXT_CFG. When the state of ABMC is changed, the MSR needs
>> to be updated on all the logical processors in the QOS Domain.
>>
>> Hardware counters will reset when ABMC state is changed.
>>
>> The ABMC feature details are documented in APM listed below [1].
>> [1] AMD64 Architecture Programmer's Manual Volume 2: System Programming
>> Publication # 24593 Revision 3.41 section 19.3.3.3 Assignable Bandwidth
>> Monitoring (ABMC).
> 
> 
>> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
>> index 05358e78147b..ca69f2e0909f 100644
>> --- a/arch/x86/kernel/cpu/resctrl/internal.h
>> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
>> @@ -658,4 +663,6 @@ void resctrl_file_fflags_init(const char *config, unsigned long fflags);
>>  void rdt_staged_configs_clear(void);
>>  bool closid_allocated(unsigned int closid);
>>  int resctrl_find_cleanest_closid(void);
>> +int resctrl_arch_mbm_cntr_assign_set(struct rdt_resource *r, bool enable);
>> +bool resctrl_arch_mbm_cntr_assign_enabled(struct rdt_resource *r);
>>  #endif /* _ASM_X86_RESCTRL_INTERNAL_H */
> 
> A minor nit - but could these be added to include/linux/resctrl.h instead?
> This is where they need to end up after the arch/fs split, and its harmless to do it from
> the beginning.

These prototypes were moved back to the internal header to follow guidance
from Boris that was received during recent software controller enhancement.
Boris advised [1] that items needed by other architecture should only be
moved to include/linux/resctrl.h when that support is added.

Reinette

[1] https://lore.kernel.org/lkml/20241209222047.GKZ1dtPxIu5_Hxs1fp@fat_crate.local/