Re: [PATCH v10 15/24] x86/resctrl: Implement resctrl_arch_config_cntr() to assign a counter with ABMC

[Reinette Chatre <reinette.chatre@intel.com>]

(andipan.das@amd.com -> sandipan.das@amd.com to stop sending undeliverable emails)

Hi Babu,

On 12/12/24 12:15 PM, 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.
> 
> Configure the counters by writing to the L3_QOS_ABMC_CFG MSR and specifying
> the counter ID, bandwidth source (RMID), and bandwidth event configuration.
> 
> Provide the interface to assign the counter ids to RMID.

Until now in this series many patches "introduced interface X" and every
time it was some new resctrl file that user space interacts with. This 
changelog starts with a context about "user to assign a hardware counter"
and ends with "Provide the interface", but there is no new user interface
in this patch. Can this be more specific about what this patch does?

> 
> 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@amd.com>
> ---

....

> ---
>  arch/x86/kernel/cpu/resctrl/internal.h |  3 ++
>  arch/x86/kernel/cpu/resctrl/rdtgroup.c | 58 ++++++++++++++++++++++++++
>  2 files changed, 61 insertions(+)
> 
> diff --git a/arch/x86/kernel/cpu/resctrl/internal.h b/arch/x86/kernel/cpu/resctrl/internal.h
> index 35bcf0e5ba7e..849bcfe4ea5b 100644
> --- a/arch/x86/kernel/cpu/resctrl/internal.h
> +++ b/arch/x86/kernel/cpu/resctrl/internal.h
> @@ -701,5 +701,8 @@ bool closid_allocated(unsigned int closid);
>  int resctrl_find_cleanest_closid(void);
>  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);
>  
>  #endif /* _ASM_X86_RESCTRL_INTERNAL_H */
> diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> index 72518e0ec2ec..e895d2415f22 100644
> --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
> @@ -1686,6 +1686,34 @@ unsigned int mon_event_config_index_get(u32 evtid)
>  	}
>  }
>  
> +struct cntr_config {
> +	struct rdt_resource *r;
> +	struct rdt_mon_domain *d;
> +	enum resctrl_event_id evtid;
> +	u32 rmid;
> +	u32 closid;
> +	u32 cntr_id;
> +	u32 val;
> +	bool assign;
> +};

I think I am missing something because it is not clear to me why this
new struct is needed. Why not just use union l3_qos_abmc_cfg?

If it is indeed needed it needs better formatting and clear descriptions,
a member like "val" is very generic.

> +
> +static void resctrl_abmc_config_one_amd(void *info)
> +{
> +	struct cntr_config *config = info;
> +	union l3_qos_abmc_cfg abmc_cfg = { 0 };
> +

reverse fir

> +	abmc_cfg.split.cfg_en = 1;
> +	abmc_cfg.split.cntr_en = config->assign ? 1 : 0;
> +	abmc_cfg.split.cntr_id = config->cntr_id;
> +	abmc_cfg.split.bw_src = config->rmid;
> +	abmc_cfg.split.bw_type = config->val;
> +
> +	wrmsrl(MSR_IA32_L3_QOS_ABMC_CFG, abmc_cfg.full);
> +
> +	resctrl_arch_reset_rmid(config->r, config->d, config->closid,
> +				config->rmid, config->evtid);
> +}
> +
>  static int mbm_config_show(struct seq_file *s, struct rdt_resource *r, u32 evtid)
>  {
>  	struct rdt_mon_domain *dom;
> @@ -1869,6 +1897,36 @@ static ssize_t mbm_local_bytes_config_write(struct kernfs_open_file *of,
>  	return ret ?: nbytes;
>  }
>  
> +/*
> + * 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);
> +	struct cntr_config config = { 0 };

Please see 29eaa7958367 ("x86/resctrl: Slightly clean-up mbm_config_show()")

> +
> +	config.r = r;
> +	config.d = d;
> +	config.evtid = evtid;
> +	config.rmid = rmid;
> +	config.closid = closid;
> +	config.cntr_id = cntr_id;
> +
> +	/* Update the event configuration from the domain */
> +	if (evtid == QOS_L3_MBM_TOTAL_EVENT_ID)
> +		config.val = hw_dom->mbm_total_cfg;
> +	else
> +		config.val = hw_dom->mbm_local_cfg;
> +
> +	config.assign = assign;
> +
> +	smp_call_function_any(&d->hdr.cpu_mask, resctrl_abmc_config_one_amd, &config, 1);
> +
> +	return 0;
> +}
> +
>  /* rdtgroup information files for one cache resource. */
>  static struct rftype res_common_files[] = {
>  	{

Reinette