[PATCH v8 07/10] fs/resctrl: Introduce interface to display io_alloc CBMs

[Babu Moger <babu.moger@amd.com>]

The io_alloc feature in resctrl enables system software to configure
the portion of the cache allocated for I/O traffic.

Add "io_alloc_cbm" resctrl file to display CBMs (Capacity Bit Mask) of
io_alloc feature.

The CBM interface file io_alloc_cbm resides in the info directory
(e.g., /sys/fs/resctrl/info/L3/). Displaying the resource name is not
necessary. Pass the resource name to show_doms() and print it only if
the name is valid. For io_alloc, pass NULL to suppress printing the
resource name.

When CDP is enabled, io_alloc routes traffic using the highest CLOSID
associated with the L3CODE resource. To ensure consistent cache allocation
behavior, the L3CODE and L3DATA resources must remain synchronized.
rdtgroup_init_cat() function takes both L3CODE and L3DATA into account when
initializing CBMs for new groups.  The io_alloc feature adheres to this
same principle, meaning that the Cache Bit Masks (CBMs) accessed through
either L3CODE or L3DATA will reflect identical values.

Signed-off-by: Babu Moger <babu.moger@amd.com>
---
v8: Updated the changelog.
    Moved resctrl_io_alloc_cbm_show() to fs/resctrl/ctrlmondata.c.
    show_doms is remains static with this change.

v7: Updated changelog.
    Updated use doc (resctrl.rst).
    Removed if (io_alloc_closid < 0) check. Not required anymore.

v6: Added "io_alloc_cbm" details in user doc resctrl.rst.
    Resource name is not printed in CBM now. Corrected the texts about it
    in resctrl.rst.

v5: Resolved conflicts due to recent resctrl FS/ARCH code restructure.
    Updated show_doms() to print the resource if only it is valid. Pass NULL while
    printing io_alloc CBM.
    Changed the code to access the CBMs via either L3CODE or L3DATA resources.

v4: Updated the change log.
    Added rdtgroup_mutex before rdt_last_cmd_puts().
    Returned -ENODEV when resource type is CDP_DATA.
    Kept the resource name while printing the CBM (L3:0=fff) that way
    I dont have to change show_doms() just for this feature and it is
    consistant across all the schemata display.

v3: Minor changes due to changes in resctrl_arch_get_io_alloc_enabled()
    and resctrl_io_alloc_closid_get().
    Added the check to verify CDP resource type.
    Updated the commit log.

v2: Fixed to display only on L3 resources.
    Added the locks while processing.
    Rename the displat to io_alloc_cbm (from sdciae_cmd).
---
 Documentation/filesystems/resctrl.rst | 19 +++++++++++++
 fs/resctrl/ctrlmondata.c              | 39 ++++++++++++++++++++++++---
 fs/resctrl/internal.h                 |  3 +++
 fs/resctrl/rdtgroup.c                 | 11 +++++++-
 4 files changed, 68 insertions(+), 4 deletions(-)

diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
index bd0a633afbb9..3002f7fdb2fe 100644
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -173,6 +173,25 @@ related to allocation:
 		available for general (CPU) cache allocation for both the L3CODE and
 		L3DATA resources.
 
+"io_alloc_cbm":
+		CBMs(Capacity Bit Masks) that describe the portions of cache instances
+		to which I/O traffic from supported I/O devices are routed when "io_alloc"
+		is enabled.
+
+		CBMs are displayed in the following format:
+
+			<cache_id0>=<cbm>;<cache_id1>=<cbm>;...
+
+		Example::
+
+			# cat /sys/fs/resctrl/info/L3/io_alloc_cbm
+			0=ffff;1=ffff
+
+		When CDP is enabled "io_alloc_cbm" associated with the DATA and CODE
+		resources may reflect the same values. For example, values read from and
+		written to /sys/fs/resctrl/info/L3DATA/io_alloc_cbm may be reflected by
+		/sys/fs/resctrl/info/L3CODE/io_alloc_cbm and vice versa.
+
 Memory bandwidth(MB) subdirectory contains the following files
 with respect to allocation:
 
diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
index bf982eab7b18..edb9dd131eed 100644
--- a/fs/resctrl/ctrlmondata.c
+++ b/fs/resctrl/ctrlmondata.c
@@ -381,7 +381,8 @@ ssize_t rdtgroup_schemata_write(struct kernfs_open_file *of,
 	return ret ?: nbytes;
 }
 
-static void show_doms(struct seq_file *s, struct resctrl_schema *schema, int closid)
+static void show_doms(struct seq_file *s, struct resctrl_schema *schema,
+		      char *resource_name, int closid)
 {
 	struct rdt_resource *r = schema->res;
 	struct rdt_ctrl_domain *dom;
@@ -391,7 +392,8 @@ static void show_doms(struct seq_file *s, struct resctrl_schema *schema, int clo
 	/* Walking r->domains, ensure it can't race with cpuhp */
 	lockdep_assert_cpus_held();
 
-	seq_printf(s, "%*s:", max_name_width, schema->name);
+	if (resource_name)
+		seq_printf(s, "%*s:", max_name_width, resource_name);
 	list_for_each_entry(dom, &r->ctrl_domains, hdr.list) {
 		if (sep)
 			seq_puts(s, ";");
@@ -437,7 +439,7 @@ int rdtgroup_schemata_show(struct kernfs_open_file *of,
 			closid = rdtgrp->closid;
 			list_for_each_entry(schema, &resctrl_schema_all, list) {
 				if (closid < schema->num_closid)
-					show_doms(s, schema, closid);
+					show_doms(s, schema, schema->name, closid);
 			}
 		}
 	} else {
@@ -822,3 +824,34 @@ ssize_t resctrl_io_alloc_write(struct kernfs_open_file *of, char *buf,
 
 	return ret ?: nbytes;
 }
+
+int resctrl_io_alloc_cbm_show(struct kernfs_open_file *of, struct seq_file *seq, void *v)
+{
+	struct resctrl_schema *s = rdt_kn_parent_priv(of->kn);
+	struct rdt_resource *r = s->res;
+	int ret = 0;
+
+	cpus_read_lock();
+	mutex_lock(&rdtgroup_mutex);
+
+	rdt_last_cmd_clear();
+
+	if (!r->cache.io_alloc_capable) {
+		rdt_last_cmd_printf("io_alloc is not supported on %s\n", s->name);
+		ret = -ENODEV;
+		goto out_unlock;
+	}
+
+	if (!resctrl_arch_get_io_alloc_enabled(r)) {
+		rdt_last_cmd_printf("io_alloc is not enabled on %s\n", s->name);
+		ret = -EINVAL;
+		goto out_unlock;
+	}
+
+	show_doms(seq, s, NULL, resctrl_io_alloc_closid(r));
+
+out_unlock:
+	mutex_unlock(&rdtgroup_mutex);
+	cpus_read_unlock();
+	return ret;
+}
diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
index 335def7af1f6..49934cd3dc40 100644
--- a/fs/resctrl/internal.h
+++ b/fs/resctrl/internal.h
@@ -389,6 +389,9 @@ enum resctrl_conf_type resctrl_peer_type(enum resctrl_conf_type my_type);
 ssize_t resctrl_io_alloc_write(struct kernfs_open_file *of, char *buf,
 			       size_t nbytes, loff_t off);
 
+int resctrl_io_alloc_cbm_show(struct kernfs_open_file *of, struct seq_file *seq,
+			      void *v);
+
 const char *rdtgroup_name_by_closid(int closid);
 
 #ifdef CONFIG_RESCTRL_FS_PSEUDO_LOCK
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index 380ebc86c748..6af8ff6c8385 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -1917,6 +1917,12 @@ static struct rftype res_common_files[] = {
 		.seq_show	= resctrl_io_alloc_show,
 		.write          = resctrl_io_alloc_write,
 	},
+	{
+		.name		= "io_alloc_cbm",
+		.mode		= 0444,
+		.kf_ops		= &rdtgroup_kf_single_ops,
+		.seq_show	= resctrl_io_alloc_cbm_show,
+	},
 	{
 		.name		= "max_threshold_occupancy",
 		.mode		= 0644,
@@ -2095,9 +2101,12 @@ static void io_alloc_init(void)
 {
 	struct rdt_resource *r = resctrl_arch_get_resource(RDT_RESOURCE_L3);
 
-	if (r->cache.io_alloc_capable)
+	if (r->cache.io_alloc_capable) {
 		resctrl_file_fflags_init("io_alloc", RFTYPE_CTRL_INFO |
 					 RFTYPE_RES_CACHE);
+		resctrl_file_fflags_init("io_alloc_cbm",
+					 RFTYPE_CTRL_INFO | RFTYPE_RES_CACHE);
+	}
 }
 
 void resctrl_file_fflags_init(const char *config, unsigned long fflags)
-- 
2.34.1