linux-kernel - Re: [PATCH v8 16/25] x86/resctrl: Implement resctrl_arch_config

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Message-ID: <d0251b1b-a188-459d-a758-fe34d91ae91b@intel.com>
Date: Tue, 15 Oct 2024 20:23:47 -0700
From: Reinette Chatre <reinette.chatre@...el.com>
To: Babu Moger <babu.moger@....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 v8 16/25] x86/resctrl: Implement
 resctrl_arch_config_cntr() to assign a counter with ABMC

Hi Babu,

On 10/9/24 10:39 AM, 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.
> 
> Counters are configured by writing to L3_QOS_ABMC_CFG MSR and
> specifying the counter id, bandwidth source, and bandwidth types.
> 
> Provide the interface to assign the counter ids to RMID.
> 
> 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>
> ---

...

> ---
>  arch/x86/kernel/cpu/resctrl/internal.h |  3 ++
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 45 ++++++++++++++++++++++++++
>  2 files changed, 48 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index 58298db9034f..6d4df0490186 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -705,6 +705,9 @@ int mbm_cntr_alloc(struct rdt_resource *r);
>  void mbm_cntr_free(struct rdt_resource *r, u32 cntr_id);
>  void arch_mbm_evt_config_init(struct rdt_hw_mon_domain *hw_dom);
>  unsigned int mon_event_config_index_get(u32 evtid);
> +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);
>  void rdt_staged_configs_clear(void);
>  bool closid_allocated(unsigned int closid);
>  int resctrl_find_cleanest_closid(void);
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 03b670b95c49..4ab1a18010c9 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -1853,6 +1853,51 @@ static ssize_t mbm_local_bytes_config_write(struct kernfs_open_file *of,
>  	return ret ?: nbytes;
>  }
>  
> +static void resctrl_abmc_config_one_amd(void *info)
> +{
> +	u64 *msrval = info;
> +
> +	wrmsrl(MSR_IA32_L3_QOS_ABMC_CFG, *msrval);
> +}
> +
> +/*
> + * 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 *arch_mbm;
> +
> +	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;
> +		arch_mbm = &hw_dom->arch_mbm_total[rmid];
> +	} else {
> +		abmc_cfg.split.bw_type = hw_dom->mbm_local_cfg;
> +		arch_mbm = &hw_dom->arch_mbm_local[rmid];
> +	}
> +
> +	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.
> +	 */
> +	if (arch_mbm)
> +		memset(arch_mbm, 0, sizeof(struct arch_mbm_state));
> +

More on this later, but I do believe later code can be simplified if
reset of architectural state is done by caller. This function should
focus on just configuring the counter.

> +	return 0;
> +}
> +
>  /* rdtgroup information files for one cache resource. */
>  static struct rftype res_common_files[] = {
>  	{

Reinette