linux-kernel - [PATCH v9 11/13] x86/resctrl: Add sysfs interface to write mbm_local_bytes

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Message-ID: <166990904243.17806.8875872967137007418.stgit@bmoger-ubuntu>
Date:   Thu, 1 Dec 2022 09:37:22 -0600
From:   Babu Moger <babu.moger@....com>
To:     <corbet@....net>, <reinette.chatre@...el.com>,
        <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>
CC:     <fenghua.yu@...el.com>, <dave.hansen@...ux.intel.com>,
        <x86@...nel.org>, <hpa@...or.com>, <paulmck@...nel.org>,
        <akpm@...ux-foundation.org>, <quic_neeraju@...cinc.com>,
        <rdunlap@...radead.org>, <damien.lemoal@...nsource.wdc.com>,
        <songmuchun@...edance.com>, <peterz@...radead.org>,
        <jpoimboe@...nel.org>, <pbonzini@...hat.com>, <babu.moger@....com>,
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        <james.morse@....com>, <linux-doc@...r.kernel.org>,
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Subject: [PATCH v9 11/13] x86/resctrl: Add sysfs interface to write
 mbm_local_bytes_config

The current event configuration for mbm_local_bytes can be changed by
the user by writing to the configuration file
/sys/fs/resctrl/info/L3_MON/mbm_local_bytes_config.

The event configuration settings are domain specific and will affect all
the CPUs in the domain.

Following are the types of events supported:
====  ===========================================================
Bits   Description
====  ===========================================================
6      Dirty Victims from the QOS domain to all types of memory
5      Reads to slow memory in the non-local NUMA domain
4      Reads to slow memory in the local NUMA domain
3      Non-temporal writes to non-local NUMA domain
2      Non-temporal writes to local NUMA domain
1      Reads to memory in the non-local NUMA domain
0      Reads to memory in the local NUMA domain
====  ===========================================================

For example:
To change the mbm_local_bytes_config to count all the non-temporal writes
on domain 0, the bits 2 and 3 needs to be set which is 1100b (in hex 0xc).
Run the command.
    $echo  0=0xc > /sys/fs/resctrl/info/L3_MON/mbm_local_bytes_config

To change the mbm_local_bytes to count only reads to local NUMA domain 1,
the bit 0 needs to be set which 1b (in hex 0x1). Run the command.
    $echo  1=0x1 > /sys/fs/resctrl/info/L3_MON/mbm_local_bytes_config

Signed-off-by: Babu Moger <babu.moger@....com>
---
 arch/x86/kernel/cpu/resctrl/rdtgroup.c |   29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 8a22a652a6e8..6897c480ae55 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -1641,6 +1641,32 @@ static ssize_t mbm_total_bytes_config_write(struct kernfs_open_file *of,
 	return ret ?: nbytes;
 }
 
+static ssize_t mbm_local_bytes_config_write(struct kernfs_open_file *of,
+					    char *buf, size_t nbytes,
+					    loff_t off)
+{
+	struct rdt_resource *r = of->kn->parent->priv;
+	int ret;
+
+	/* Valid input requires a trailing newline */
+	if (nbytes == 0 || buf[nbytes - 1] != '\n')
+		return -EINVAL;
+
+	cpus_read_lock();
+	mutex_lock(&rdtgroup_mutex);
+
+	rdt_last_cmd_clear();
+
+	buf[nbytes - 1] = '\0';
+
+	ret = mon_config_write(r, buf, QOS_L3_MBM_LOCAL_EVENT_ID);
+
+	mutex_unlock(&rdtgroup_mutex);
+	cpus_read_unlock();
+
+	return ret ?: nbytes;
+}
+
 /* rdtgroup information files for one cache resource. */
 static struct rftype res_common_files[] = {
 	{
@@ -1748,9 +1774,10 @@ static struct rftype res_common_files[] = {
 	},
 	{
 		.name		= "mbm_local_bytes_config",
-		.mode		= 0444,
+		.mode		= 0644,
 		.kf_ops		= &rdtgroup_kf_single_ops,
 		.seq_show	= mbm_local_bytes_config_show,
+		.write		= mbm_local_bytes_config_write,
 	},
 	{
 		.name		= "cpus",