[PATCH v4 17/19] x86/resctrl: Introduce the interface switch between ABMC and mbm_legacy

Babu Moger
2024-05-24T12:26:13Z

Introduce interface to switch between ABMC and legacy_mbm modes.

By default ABMC is enabled on resctrl mount if the feature is available.
However, user will have the option to go back to legacy_mbm if required.

$ cat /sys/fs/resctrl/info/L3_MON/mbm_assign
[abmc]
mbm_legacy

To enable the legacy monitoring feature:
$ echo "mbm_legacy" > /sys/fs/resctrl/info/L3_MON/mbm_assign

Signed-off-by: Babu Moger <babu.moger@amd.com>
---
v4: Minor commit text changes. Keep the default to ABMC when supported.

v3: New patch to address the review comments from upstream.
---
Documentation/arch/x86/resctrl.rst | 10 +++++++
arch/x86/kernel/cpu/resctrl/rdtgroup.c | 40 +++++++++++++++++++++++++-
2 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/Documentation/arch/x86/resctrl.rst b/Documentation/arch/x86/resctrl.rst
index ab3cde61a124..fd050d4d22cd 100644
--- a/Documentation/arch/x86/resctrl.rst
+++ b/Documentation/arch/x86/resctrl.rst
@@ -271,6 +271,16 @@ with the following files:
[abmc]
mbm_legacy

+ * To enable ABMC feature:
+ ::
+
+ # echo "abmc" > /sys/fs/resctrl/info/L3_MON/mbm_assign
+
+ * To enable the legacy monitoring feature:
+ ::
+
+ # echo "mbm_legacy" > /sys/fs/resctrl/info/L3_MON/mbm_assign
+
"max_threshold_occupancy":
Read/write file provides the largest value (in
bytes) at which a previously used LLC_occupancy
diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index f452b6d9bb99..d77ff059269a 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -908,6 +908,43 @@ static int rdtgroup_mbm_assign_show(struct kernfs_open_file *of,
return 0;
}

+/*
+ * rdtgroup_mode_write - Modify the resource group's mode
+ */
+static ssize_t rdtgroup_mbm_assign_write(struct kernfs_open_file *of,
+ char *buf, size_t nbytes,
+ loff_t off)
+{
+ struct rdt_resource *r = of->kn->parent->priv;
+ int ret = 0;
+
+ if (!r->abmc_capable)
+ return -EINVAL;
+
+ /* Valid input requires a trailing newline */
+ if (nbytes == 0 || buf[nbytes - 1] != '\n')
+ return -EINVAL;
+
+ buf[nbytes - 1] = '\0';
+
+ cpus_read_lock();
+ mutex_lock(&rdtgroup_mutex);
+
+ rdt_last_cmd_clear();
+
+ if (!strcmp(buf, "mbm_legacy"))
+ resctrl_abmc_disable(RDT_RESOURCE_L3);
+ else if (!strcmp(buf, "abmc"))
+ ret = resctrl_abmc_enable(RDT_RESOURCE_L3);
+ else
+ ret = -EINVAL;
+
+ mutex_unlock(&rdtgroup_mutex);
+ cpus_read_unlock();
+
+ return ret ?: nbytes;
+}
+
#ifdef CONFIG_PROC_CPU_RESCTRL

/*
@@ -2087,9 +2124,10 @@ static struct rftype res_common_files[] = {
},
{
.name = "mbm_assign",
- .mode = 0444,
+ .mode = 0644,
.kf_ops = &rdtgroup_kf_single_ops,
.seq_show = rdtgroup_mbm_assign_show,
+ .write = rdtgroup_mbm_assign_write,
},
{
.name = "cpus",
--
2.34.1