Commit 8e931105 authored by Tony Luck's avatar Tony Luck Committed by Borislav Petkov (AMD)
Browse files

x86/resctrl: Add write option to "mba_MBps_event" file 



The "mba_MBps" mount option provides an alternate method to control memory
bandwidth. Instead of specifying allowable bandwidth as a percentage of
maximum possible, the user provides a MiB/s limit value.

There is a file in each CTRL_MON group directory that shows the event
currently in use.

Allow writing that file to choose a different event.

A user can choose any of the memory bandwidth monitoring events listed in
/sys/fs/resctrl/info/L3_mon/mon_features independently for each CTRL_MON group
by writing to each of the "mba_MBps_event" files.

Signed-off-by: default avatarTony Luck <tony.luck@intel.com>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: default avatarReinette Chatre <reinette.chatre@intel.com>
Tested-by: default avatarBabu Moger <babu.moger@amd.com>
Link: https://lore.kernel.org/r/20241206163148.83828-8-tony.luck@intel.com
parent f5cd0e31

arch/x86/kernel/cpu/resctrl/ctrlmondata.c

+40 −0
Original line number Diff line number Diff line
@@ -518,6 +518,46 @@ static int smp_mon_event_count(void *arg) 
	return 0;

}



ssize_t rdtgroup_mba_mbps_event_write(struct kernfs_open_file *of,

				      char *buf, size_t nbytes, loff_t off)

{

	struct rdtgroup *rdtgrp;

	int ret = 0;



	/* Valid input requires a trailing newline */

	if (nbytes == 0 || buf[nbytes - 1] != '\n')

		return -EINVAL;

	buf[nbytes - 1] = '\0';



	rdtgrp = rdtgroup_kn_lock_live(of->kn);

	if (!rdtgrp) {

		rdtgroup_kn_unlock(of->kn);

		return -ENOENT;

	}

	rdt_last_cmd_clear();



	if (!strcmp(buf, "mbm_local_bytes")) {

		if (is_mbm_local_enabled())

			rdtgrp->mba_mbps_event = QOS_L3_MBM_LOCAL_EVENT_ID;

		else

			ret = -EINVAL;

	} else if (!strcmp(buf, "mbm_total_bytes")) {

		if (is_mbm_total_enabled())

			rdtgrp->mba_mbps_event = QOS_L3_MBM_TOTAL_EVENT_ID;

		else

			ret = -EINVAL;

	} else {

		ret = -EINVAL;

	}



	if (ret)

		rdt_last_cmd_printf("Unsupported event id '%s'\n", buf);



	rdtgroup_kn_unlock(of->kn);



	return ret ?: nbytes;

}



int rdtgroup_mba_mbps_event_show(struct kernfs_open_file *of,

				 struct seq_file *s, void *v)

{

arch/x86/kernel/cpu/resctrl/internal.h

+2 −0
Original line number Diff line number Diff line
@@ -610,6 +610,8 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of, 
				char *buf, size_t nbytes, loff_t off);

int rdtgroup_schemata_show(struct kernfs_open_file *of,

			   struct seq_file *s, void *v);

ssize_t rdtgroup_mba_mbps_event_write(struct kernfs_open_file *of,

				      char *buf, size_t nbytes, loff_t off);

int rdtgroup_mba_mbps_event_show(struct kernfs_open_file *of,

				 struct seq_file *s, void *v);

bool rdtgroup_cbm_overlaps(struct resctrl_schema *s, struct rdt_ctrl_domain *d,

arch/x86/kernel/cpu/resctrl/rdtgroup.c

+2 −1
Original line number Diff line number Diff line
@@ -1952,8 +1952,9 @@ static struct rftype res_common_files[] = { 
	},

	{

		.name		= "mba_MBps_event",

		.mode		= 0444,

		.mode		= 0644,

		.kf_ops		= &rdtgroup_kf_single_ops,

		.write		= rdtgroup_mba_mbps_event_write,

		.seq_show	= rdtgroup_mba_mbps_event_show,

	},

	{