[RFC PATCH 1/8] fs/resctrl: Change UI of "max" file (merge back into earlier patches)

[Tony Luck]

Make the UI of the "max" file show values per-domain so no changes
in UI are needed when support for asymmetric controls (L2 on hybrid
CPUs) is added later.

Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
---
 Documentation/filesystems/resctrl.rst |  5 ++++-
 fs/resctrl/rdtgroup.c                 | 27 ++++++++++++++++++++-------
 2 files changed, 24 insertions(+), 8 deletions(-)

diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
index 434e6f42db4a..de162280a0fe 100644
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -397,12 +397,15 @@ with individual files:
 		the schemata file.
 
 "max":
+	Maximum values per domain in the same format as the schemata file.
+	Format of values depends on the type of the control:
+
 	When "type" == "scalar":
 		The maximum value that can be written to the control when writing
 		the schemata file.
 
 	When "type" == "bitmap":
-		The supported bitmap (in hexadecimal with 0x prefix) with
+		The supported bitmap (in hexadecimal without 0x prefix) with
 		all bits set.
 
 "tolerance":
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index 416b73c57016..7119ad0029c1 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -2465,15 +2465,28 @@ static int resctrl_ctrl_max_show(struct kernfs_open_file *of,
 				 struct seq_file *seq, void *v)
 {
 	struct resctrl_ctrl *ctrl = rdt_kn_parent_priv(of->kn);
+	struct rdt_ctrl_domain *d;
+	bool sep = false;
 
-	switch (ctrl->type) {
-	case RESCTRL_CTRL_SCALAR:
-		seq_printf(seq, "%u\n", ctrl->scalar.max);
-		break;
-	case RESCTRL_CTRL_BITMAP:
-		seq_printf(seq, "0x%lx\n", BIT_MASK(ctrl->bitmap.cbm_len) - 1);
-		break;
+	if (!info_kn_lock(of->kn))
+		return -ENOENT;
+
+	list_for_each_entry_rcu(d, &ctrl->domains, hdr.list, lockdep_is_cpus_held()) {
+		if (sep)
+			seq_putc(seq, ';');
+		switch (ctrl->type) {
+		case RESCTRL_CTRL_SCALAR:
+			seq_printf(seq, "%d=%u", d->hdr.id, ctrl->scalar.max);
+			break;
+		case RESCTRL_CTRL_BITMAP:
+			seq_printf(seq, "%d=%lx", d->hdr.id, BIT_MASK(ctrl->bitmap.cbm_len) - 1);
+			break;
+		}
+		sep = true;
 	}
+	seq_putc(seq, '\n');
+
+	info_kn_unlock(of->kn);
 
 	return 0;
 }
-- 
2.56.0