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Message-ID: <549a772b83461fb4cb7b6e8dabc60724cbe96ad0.1756851697.git.babu.moger@amd.com>
Date: Tue, 2 Sep 2025 17:41:32 -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>,
<mingo@...hat.com>, <bp@...en8.de>, <dave.hansen@...ux.intel.com>
CC: <x86@...nel.org>, <hpa@...or.com>, <kas@...nel.org>,
<rick.p.edgecombe@...el.com>, <akpm@...ux-foundation.org>,
<paulmck@...nel.org>, <pmladek@...e.com>,
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<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<linux-coco@...ts.linux.dev>, <kvm@...r.kernel.org>
Subject: [PATCH v9 10/10] 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 bit_usage representation to reflect the io_alloc configuration.
Revise the documentation for "shareable_bits" and "bit_usage" to reflect
the impact of io_alloc feature.
Signed-off-by: Babu Moger <babu.moger@....com>
---
v9: Changelog update.
Added code comments about CDP.
Updated the "bit_usage" section of resctrl.rst for io_alloc.
v8: Moved the patch to last after all the concepts are initialized.
Updated user doc resctrl.rst.
Simplified the CDT check in rdt_bit_usage_show() as CDP_DATA and CDP_CODE
are in sync with io_alloc enabled.
v7: New patch split from earlier patch #5.
Added resctrl_io_alloc_closid() to return max COSID.
---
Documentation/filesystems/resctrl.rst | 35 ++++++++++++++++-----------
fs/resctrl/ctrlmondata.c | 2 +-
fs/resctrl/internal.h | 2 ++
fs/resctrl/rdtgroup.c | 21 ++++++++++++++--
4 files changed, 43 insertions(+), 17 deletions(-)
diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
index 7e3eda324de5..72ea6f3f36bc 100644
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -90,12 +90,19 @@ 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" is enabled, a portion of each cache instance 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 via io_alloc_cbm.
+
"bit_usage":
Annotated capacity bitmasks showing how all
instances of the resource are used. The legend is:
@@ -109,16 +116,16 @@ related to allocation:
"H":
Corresponding region is used by hardware only
but available for software use. If a resource
- has bits set in "shareable_bits" but not all
- of these bits appear in the resource groups'
- schematas then the bits appearing in
- "shareable_bits" but no resource group will
- be marked as "H".
+ has bits set in "shareable_bits" or "io_alloc_cbm"
+ but not all of these bits appear in the resource
+ groups' schematas then the bits appearing in
+ "shareable_bits" or "io_alloc_cbm" but no
+ resource group will be marked as "H".
"X":
Corresponding region is available for sharing and
- used by hardware and software. These are the
- bits that appear in "shareable_bits" as
- well as a resource group's allocation.
+ used by hardware and software. These are the bits
+ that appear in "shareable_bits" or "io_alloc_cbm"
+ as well as a resource group's allocation.
"S":
Corresponding region is used by software
and available for sharing.
diff --git a/fs/resctrl/ctrlmondata.c b/fs/resctrl/ctrlmondata.c
index 791ecb559b50..1118054fdc2c 100644
--- a/fs/resctrl/ctrlmondata.c
+++ b/fs/resctrl/ctrlmondata.c
@@ -738,7 +738,7 @@ static int resctrl_io_alloc_init_cbm(struct resctrl_schema *s, u32 closid)
* 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)
+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;
diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
index 5467c3ad1b6d..98b87725508b 100644
--- a/fs/resctrl/internal.h
+++ b/fs/resctrl/internal.h
@@ -395,6 +395,8 @@ int resctrl_io_alloc_cbm_show(struct kernfs_open_file *of, struct seq_file *seq,
ssize_t resctrl_io_alloc_cbm_write(struct kernfs_open_file *of, char *buf,
size_t nbytes, loff_t off);
+u32 resctrl_io_alloc_closid(struct rdt_resource *r);
+
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 ddac021c02d8..951d44d6f488 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -1068,15 +1068,17 @@ 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);
@@ -1104,6 +1106,21 @@ 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.
+ * Also, when CDP is enabled the CBMs of L3CODE and L3DATA are kept
+ * in sync. So, the CBMs for "io_alloc" can be accessed through either
+ * L3CODE or L3DATA.
+ */
+ if (resctrl_arch_get_io_alloc_enabled(r)) {
+ ctrl_val = resctrl_arch_get_config(r, dom,
+ resctrl_io_alloc_closid(r),
+ s->conf_type);
+ 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
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