[PATCH v7 10/12] x86/resctrl: Add sysfs interface to write mbm_local_bytes event configuration

[Babu Moger]

The current event configuration can be changed by the user by writing
to the configuration file /sys/fs/resctrl/info/L3_MON/mbm_local_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 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_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_config

Signed-off-by: Babu Moger <babu.moger@xxxxxxx>
---
 arch/x86/kernel/cpu/resctrl/rdtgroup.c |   21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 25ff56ecb817..e744db5dc057 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -1639,6 +1639,26 @@ static ssize_t mbm_total_config_write(struct kernfs_open_file *of,
 	return ret ?: nbytes;
 }
 
+static ssize_t mbm_local_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;
+
+	rdt_last_cmd_clear();
+
+	buf[nbytes - 1] = '\0';
+
+	ret = mon_config_parse(r, buf, QOS_L3_MBM_LOCAL_EVENT_ID);
+
+	return ret ?: nbytes;
+}
+
 /* rdtgroup information files for one cache resource. */
 static struct rftype res_common_files[] = {
 	{
@@ -1749,6 +1769,7 @@ static struct rftype res_common_files[] = {
 		.mode		= 0644,
 		.kf_ops		= &rdtgroup_kf_single_ops,
 		.seq_show	= mbm_local_config_show,
+		.write		= mbm_local_config_write,
 	},
 	{
 		.name		= "cpus",