linux-kernel - Re: [PATCH v11 14/23] x86/resctrl: Implement resctrl_arch_config

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Message-ID: <43c7dc71-3fa6-48ef-89ef-518580996ac8@amd.com>
Date: Wed, 19 Feb 2025 15:00:31 -0600
From: "Moger, Babu" <babu.moger@....com>
To: Dave Martin <Dave.Martin@....com>
Cc: corbet@....net, reinette.chatre@...el.com, tglx@...utronix.de,
 mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
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Subject: Re: [PATCH v11 14/23] x86/resctrl: Implement
 resctrl_arch_config_cntr() to assign a counter with ABMC

Hi Dave,

On 2/19/25 07:32, Dave Martin wrote:
> On Wed, Jan 22, 2025 at 02:20:22PM -0600, Babu Moger wrote:
>> The ABMC feature provides an option to the user to assign a hardware
>> counter to an RMID, event pair and monitor the bandwidth as long as it
>> is assigned. The assigned RMID will be tracked by the hardware until the
>> user unassigns it manually.
>>
>> Implement an architecture-specific handler to assign and unassign the
>> counter. Configure counters by writing to the L3_QOS_ABMC_CFG MSR,
>> specifying the counter ID, bandwidth source (RMID), and event
>> configuration.
>>
>> The feature details are documented in the 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).
>>
>> Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
>> Signed-off-by: Babu Moger <babu.moger@....com>
>> ---
> 
> [...]
> 
>> diff --git a/arch/x86/kernel/cpu/resctrl/monitor.c b/arch/x86/kernel/cpu/resctrl/monitor.c
>> index f2bf5b13465d..ef836bb69b9b 100644
>> --- a/arch/x86/kernel/cpu/resctrl/monitor.c
>> +++ b/arch/x86/kernel/cpu/resctrl/monitor.c
>> @@ -1371,3 +1371,45 @@ void resctrl_arch_mon_event_config_set(void *info)
> 
> [...]
> 
>> +/*
>> + * Send an IPI to the domain to assign the counter to RMID, event pair.
>> + */
>> +int resctrl_arch_config_cntr(struct rdt_resource *r, struct rdt_mon_domain *d,
>> +			     enum resctrl_event_id evtid, u32 rmid, u32 closid,
>> +			     u32 cntr_id, bool assign)
>> +{
>> +	struct rdt_hw_mon_domain *hw_dom = resctrl_to_arch_mon_dom(d);
>> +	union l3_qos_abmc_cfg abmc_cfg = { 0 };
>> +	struct arch_mbm_state *am;
>> +
>> +	abmc_cfg.split.cfg_en = 1;
>> +	abmc_cfg.split.cntr_en = assign ? 1 : 0;
>> +	abmc_cfg.split.cntr_id = cntr_id;
>> +	abmc_cfg.split.bw_src = rmid;
>> +
>> +	/* Update the event configuration from the domain */
>> +	if (evtid == QOS_L3_MBM_TOTAL_EVENT_ID)
>> +		abmc_cfg.split.bw_type = hw_dom->mbm_total_cfg;
>> +	else
>> +		abmc_cfg.split.bw_type = hw_dom->mbm_local_cfg;
>> +
>> +	smp_call_function_any(&d->hdr.cpu_mask, resctrl_abmc_config_one_amd, &abmc_cfg, 1);
>> +
>> +	/*
>> +	 * Reset the architectural state so that reading of hardware
>> +	 * counter is not considered as an overflow in next update.
>> +	 */
>> +	am = get_arch_mbm_state(hw_dom, rmid, evtid);
> 
> Is this necessary when unassigning the counter, or only when assigning?

Yes. It is only required when assigning. Will add a check. thanks


> 
>> +	if (am)
>> +		memset(am, 0, sizeof(*am));
>> +
>> +	return 0;
>> +}
> 
> [...]
> 
> Cheers
> ---Dave
> 

-- 
Thanks
Babu Moger