linux-kernel - [PATCH v7 05/10] fs/resctrl: Update bit_usage to reflect io

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Message-ID: <87e1a53201f3e539fc917a5d901f09bce432f720.1752167718.git.babu.moger@amd.com>
Date: Thu, 10 Jul 2025 12:16:19 -0500
From: Babu Moger <babu.moger@....com>
To: <corbet@....net>, <tony.luck@...el.com>, <reinette.chatre@...el.com>,
	<Dave.Martin@....com>, <james.morse@....com>, <tglx@...utronix.de>,
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Subject: [PATCH v7 05/10] fs/resctrl: Update bit_usage to reflect io_alloc

When the io_alloc feature is enabled, a portion of the cache can be
configured for shared use between hardware and software.

Update the bit_usage representation to reflect the io_alloc configuration.

Signed-off-by: Babu Moger <babu.moger@....com>
---
v7: New patch split from earlier patch #5.
    Added resctrl_io_alloc_closid() to return max COSID.
---
 Documentation/filesystems/resctrl.rst | 20 ++++++++++-----
 fs/resctrl/rdtgroup.c                 | 37 +++++++++++++++++++++++++--
 2 files changed, 49 insertions(+), 8 deletions(-)

diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
index c7949dd44f2f..c3c412733632 100644
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -89,12 +89,20 @@ related to allocation:
 		must be set when writing a mask.
 
 "shareable_bits":
-		Bitmask of shareable resource with other executing
-		entities (e.g. I/O). User can use this when
-		setting up exclusive cache partitions. Note that
-		some platforms support devices that have their
-		own settings for cache use which can over-ride
-		these bits.
+		Bitmask of shareable resource with other executing entities
+		(e.g. I/O). Applies to all instances of this resource. User
+		can use this when setting up exclusive cache partitions.
+		Note that some platforms support devices that have their
+		own settings for cache use which can over-ride these bits.
+
+		When "io_alloc" feature is enabled, a portion of the cache
+		can be configured for shared use between hardware and software.
+
+		"bit_usage" should be used to see which portions of each cache
+		instance is configured for hardware use via "io_alloc" feature
+		because every cache instance can have its "io_alloc" bitmask
+		configured independently.
+
 "bit_usage":
 		Annotated capacity bitmasks showing how all
 		instances of the resource are used. The legend is:
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index 77d08229d855..a2eea85aecc8 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -1030,6 +1030,20 @@ static int rdt_shareable_bits_show(struct kernfs_open_file *of,
 	return 0;
 }
 
+/*
+ * resctrl_io_alloc_closid() - io_alloc feature routes I/O traffic using
+ * the highest available CLOSID. Retrieve the maximum CLOSID supported by the
+ * resource. Note that if Code Data Prioritization (CDP) is enabled, the number
+ * of available CLOSIDs is reduced by half.
+ */
+static u32 resctrl_io_alloc_closid(struct rdt_resource *r)
+{
+	if (resctrl_arch_get_cdp_enabled(r->rid))
+		return resctrl_arch_get_num_closid(r) / 2  - 1;
+	else
+		return resctrl_arch_get_num_closid(r) - 1;
+}
+
 /*
  * rdt_bit_usage_show - Display current usage of resources
  *
@@ -1063,15 +1077,17 @@ static int rdt_bit_usage_show(struct kernfs_open_file *of,
 
 	cpus_read_lock();
 	mutex_lock(&rdtgroup_mutex);
-	hw_shareable = r->cache.shareable_bits;
 	list_for_each_entry(dom, &r->ctrl_domains, hdr.list) {
 		if (sep)
 			seq_putc(seq, ';');
+		hw_shareable = r->cache.shareable_bits;
 		sw_shareable = 0;
 		exclusive = 0;
 		seq_printf(seq, "%d=", dom->hdr.id);
 		for (i = 0; i < closids_supported(); i++) {
-			if (!closid_allocated(i))
+			if (!closid_allocated(i) ||
+			    (resctrl_arch_get_io_alloc_enabled(r) &&
+			     i == resctrl_io_alloc_closid(r)))
 				continue;
 			ctrl_val = resctrl_arch_get_config(r, dom, i,
 							   s->conf_type);
@@ -1099,6 +1115,23 @@ static int rdt_bit_usage_show(struct kernfs_open_file *of,
 				break;
 			}
 		}
+
+		/*
+		 * When the "io_alloc" feature is enabled, a portion of the
+		 * cache is configured for shared use between hardware and software.
+		 */
+		if (resctrl_arch_get_io_alloc_enabled(r)) {
+			if (resctrl_arch_get_cdp_enabled(r->rid))
+				ctrl_val = resctrl_arch_get_config(r, dom,
+								   resctrl_io_alloc_closid(r),
+								   CDP_CODE);
+			else
+				ctrl_val = resctrl_arch_get_config(r, dom,
+								   resctrl_io_alloc_closid(r),
+								   CDP_NONE);
+			hw_shareable |= ctrl_val;
+		}
+
 		for (i = r->cache.cbm_len - 1; i >= 0; i--) {
 			pseudo_locked = dom->plr ? dom->plr->cbm : 0;
 			hwb = test_bit(i, &hw_shareable);
-- 
2.34.1