[PATCH 2/3] x86/resctrl: Add sparse_bitmaps file in info

[Wieczor-Retman, Maciej]

From: Fenghua Yu <fenghua.yu@xxxxxxxxx>

Add the interface in resctrl FS to show if sparse CAT bitmaps are
supported on the platform. Reading the file returns either a "1" if
non-contiguous 1s are supported and "0" otherwise. The file path is
/sys/fs/resctrl/info/{resource}/sparse_bitmaps, where {resource} can be
either "L2" or "L3" depending on their support in the CAT feature.

Signed-off-by: Fenghua Yu <fenghua.yu@xxxxxxxxx>
Signed-off-by: Wieczor-Retman, Maciej <maciej.wieczor-retman@xxxxxxxxx>
---
 arch/x86/kernel/cpu/resctrl/rdtgroup.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
index 725344048f85..4d27354f3f30 100644
--- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c
+++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c
@@ -895,6 +895,17 @@ static int rdt_shareable_bits_show(struct kernfs_open_file *of,
 	return 0;
 }
 
+static int rdt_has_sparse_bitmaps_show(struct kernfs_open_file *of,
+				       struct seq_file *seq, void *v)
+{
+	struct resctrl_schema *s = of->kn->parent->priv;
+	struct rdt_resource *r = s->res;
+
+	seq_printf(seq, "%u\n", r->cache.arch_has_sparse_bitmaps);
+
+	return 0;
+}
+
 /**
  * rdt_bit_usage_show - Display current usage of resources
  *
@@ -1839,6 +1850,13 @@ static struct rftype res_common_files[] = {
 		.seq_show	= rdtgroup_size_show,
 		.fflags		= RF_CTRL_BASE,
 	},
+	{
+		.name		= "sparse_bitmaps",
+		.mode		= 0444,
+		.kf_ops		= &rdtgroup_kf_single_ops,
+		.seq_show	= rdt_has_sparse_bitmaps_show,
+		.fflags		= RF_CTRL_INFO | RFTYPE_RES_CACHE,
+	},
 
 };
 
-- 
2.42.0