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Message-ID: <a47ba310e232e01d9d892ea30d570f73de3f8d8d.1761090860.git.babu.moger@amd.com>
Date: Tue, 21 Oct 2025 18:54:48 -0500
From: Babu Moger <babu.moger@....com>
To: <tony.luck@...el.com>, <reinette.chatre@...el.com>, <tglx@...utronix.de>,
<mingo@...hat.com>, <bp@...en8.de>, <dave.hansen@...ux.intel.com>
CC: <corbet@....net>, <Dave.Martin@....com>, <james.morse@....com>,
<babu.moger@....com>, <x86@...nel.org>, <hpa@...or.com>,
<akpm@...ux-foundation.org>, <paulmck@...nel.org>, <rdunlap@...radead.org>,
<pmladek@...e.com>, <kees@...nel.org>, <arnd@...db.de>, <fvdl@...gle.com>,
<seanjc@...gle.com>, <pawan.kumar.gupta@...ux.intel.com>, <xin@...or.com>,
<thomas.lendacky@....com>, <sohil.mehta@...el.com>, <jarkko@...nel.org>,
<chang.seok.bae@...el.com>, <ebiggers@...gle.com>,
<elena.reshetova@...el.com>, <ak@...ux.intel.com>,
<mario.limonciello@....com>, <perry.yuan@....com>,
<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<peternewman@...gle.com>
Subject: [PATCH v10 05/10] fs/resctrl: Introduce interface to display "io_alloc" support
Introduce the "io_alloc" resctrl file to the "info" area of a cache
resource, for example /sys/fs/resctrl/info/L3/io_alloc. "io_alloc"
indicates support for the "io_alloc" feature that allows direct insertion
of data from I/O devices into the cache.
Restrict exposing support for "io_alloc" to the L3 resource that is the
only resource where this feature can be backed by AMD's L3 Smart Data Cache
Injection Allocation Enforcement (SDCIAE). With that, the "io_alloc" file
is only visible to user space if the L3 resource supports "io_alloc". Doing
so makes the file visible for all cache resources though, for example also
L2 cache (if it supports cache allocation). As a consequence, add
capability for file to report expected "enabled" and "disabled", as well as
"not supported".
Signed-off-by: Babu Moger <babu.moger@....com>
---
v10: Changelog update.
Removed the h/w specific details from this patch and will add to the next patch.
v9: Minor user doc(resctrl.rst) update.
v8: Updated Documentation/filesystems/resctrl.rst.
Moved resctrl_io_alloc_show() to fs/resctrl/ctrlmondata.c.
Added prototype for rdt_kn_parent_priv() in fs/resctrl/internal.h
so, it can be uses in other fs/resctrl/ files.
Added comment for io_alloc_init().
v7: Updated the changelog.
Updated user doc for io_alloc in resctrl.rst.
Added mutex rdtgroup_mutex in resctrl_io_alloc_show();
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 | 15 +++++++++++++++
fs/resctrl/ctrlmondata.c | 21 +++++++++++++++++++++
fs/resctrl/internal.h | 1 +
fs/resctrl/rdtgroup.c | 22 ++++++++++++++++++++++
4 files changed, 59 insertions(+)
diff --git a/Documentation/filesystems/resctrl.rst b/Documentation/filesystems/resctrl.rst
index d7a51cae6b26..108995640ca5 100644
--- a/Documentation/filesystems/resctrl.rst
+++ b/Documentation/filesystems/resctrl.rst
@@ -137,6 +137,21 @@ related to allocation:
"1":
Non-contiguous 1s value in CBM is supported.
+"io_alloc":
+ "io_alloc" enables system software to configure the portion of
+ the cache allocated for I/O traffic. File may only exist if the
+ system supports this feature on some of its cache resources.
+
+ "disabled":
+ Resource supports "io_alloc" but the feature is disabled.
+ Portions of cache used for allocation of I/O traffic cannot
+ be configured.
+ "enabled":
+ Portions of cache used for allocation of I/O traffic
+ can be configured using "io_alloc_cbm".
+ "not supported":
+ Support not available for this resource.
+
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 0d0ef54fc4de..78a8e7b4ba24 100644
--- a/fs/resctrl/ctrlmondata.c
+++ b/fs/resctrl/ctrlmondata.c
@@ -676,3 +676,24 @@ int rdtgroup_mondata_show(struct seq_file *m, void *arg)
rdtgroup_kn_unlock(of->kn);
return ret;
}
+
+int resctrl_io_alloc_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;
+
+ mutex_lock(&rdtgroup_mutex);
+
+ if (r->cache.io_alloc_capable) {
+ if (resctrl_arch_get_io_alloc_enabled(r))
+ seq_puts(seq, "enabled\n");
+ else
+ seq_puts(seq, "disabled\n");
+ } else {
+ seq_puts(seq, "not supported\n");
+ }
+
+ mutex_unlock(&rdtgroup_mutex);
+
+ return 0;
+}
diff --git a/fs/resctrl/internal.h b/fs/resctrl/internal.h
index cf1fd82dc5a9..a18ed8889396 100644
--- a/fs/resctrl/internal.h
+++ b/fs/resctrl/internal.h
@@ -426,6 +426,7 @@ int mbm_L3_assignments_show(struct kernfs_open_file *of, struct seq_file *s, voi
ssize_t mbm_L3_assignments_write(struct kernfs_open_file *of, char *buf, size_t nbytes,
loff_t off);
+int resctrl_io_alloc_show(struct kernfs_open_file *of, struct seq_file *seq, void *v);
#ifdef CONFIG_RESCTRL_FS_PSEUDO_LOCK
int rdtgroup_locksetup_enter(struct rdtgroup *rdtgrp);
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index 0320360cd7a6..6d89160ebd11 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -1947,6 +1947,12 @@ static struct rftype res_common_files[] = {
.kf_ops = &rdtgroup_kf_single_ops,
.seq_show = rdt_thread_throttle_mode_show,
},
+ {
+ .name = "io_alloc",
+ .mode = 0444,
+ .kf_ops = &rdtgroup_kf_single_ops,
+ .seq_show = resctrl_io_alloc_show,
+ },
{
.name = "max_threshold_occupancy",
.mode = 0644,
@@ -2138,6 +2144,20 @@ static void thread_throttle_mode_init(void)
RFTYPE_CTRL_INFO | RFTYPE_RES_MB);
}
+/*
+ * The resctrl file "io_alloc" is added using L3 resource. However, it results
+ * in this file being visible for *all* cache resources (eg. L2 cache),
+ * whether it supports "io_alloc" or not.
+ */
+static void io_alloc_init(void)
+{
+ struct rdt_resource *r = resctrl_arch_get_resource(RDT_RESOURCE_L3);
+
+ if (r->cache.io_alloc_capable)
+ resctrl_file_fflags_init("io_alloc", RFTYPE_CTRL_INFO |
+ RFTYPE_RES_CACHE);
+}
+
void resctrl_file_fflags_init(const char *config, unsigned long fflags)
{
struct rftype *rft;
@@ -4408,6 +4428,8 @@ int resctrl_init(void)
thread_throttle_mode_init();
+ io_alloc_init();
+
ret = resctrl_mon_resource_init();
if (ret)
return ret;
--
2.34.1
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