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

Babu Moger
2022-10-17T22:28:49Z

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@amd.com>
---
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",