| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <2a0e6b85b06fef2d77ddd6879dea4335aeb3021f.1759312886.git.epetron@amazon.de>
Date: Fri, 3 Oct 2025 09:00:41 +0000
From: Evangelos Petrongonas <epetron@...zon.de>
To: Bjorn Helgaas <bhelgaas@...gle.com>, Alex Williamson
<alex.williamson@...hat.com>, "Rafael J . Wysocki" <rafael@...nel.org>, "Len
Brown" <lenb@...nel.org>
CC: Evangelos Petrongonas <epetron@...zon.de>, Pasha Tatashin
<pasha.tatashin@...een.com>, David Matlack <dmatlack@...gle.com>, "Vipin
Sharma" <vipinsh@...gle.com>, Chris Li <chrisl@...nel.org>, Jason Miu
<jasonmiu@...gle.com>, Pratyush Yadav <pratyush@...nel.org>, "Stanislav
Spassov" <stanspas@...zon.de>, <linux-pci@...r.kernel.org>,
<linux-acpi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<nh-open-source@...zon.com>
Subject: [RFC PATCH 05/13] pci: pcsc: control the cache via sysfs and kernel params
Add kernel parameters and runtime control mechanisms for the PCSC
A new kernel parameter 'pcsc_enabled' allows enabling or disabling
the cache at boot time. The parameter defaults to disabled.
A sysfs interface at /sys/bus/pci/pcsc/enabled provides:
- Read access to query current cache status (1=enabled, 0=disabled)
- Write access to dynamically enable/disable the cache at runtime
Signed-off-by: Evangelos Petrongonas <epetron@...zon.de>
---
Documentation/ABI/testing/sysfs-bus-pci-pcsc | 20 ++++
.../admin-guide/kernel-parameters.txt | 3 +
drivers/pci/pcsc.c | 93 ++++++++++++++++++-
3 files changed, 114 insertions(+), 2 deletions(-)
create mode 100644 Documentation/ABI/testing/sysfs-bus-pci-pcsc
diff --git a/Documentation/ABI/testing/sysfs-bus-pci-pcsc b/Documentation/ABI/testing/sysfs-bus-pci-pcsc
new file mode 100644
index 000000000000..ee92bf087816
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-bus-pci-pcsc
@@ -0,0 +1,20 @@
+PCI Configuration Space Cache (PCSC)
+-------------------------------------
+
+The PCI Configuration Space Cache (PCSC) is a transparent caching layer
+that intercepts configuration space operations to reduce hardware access
+overhead. This subsystem addresses performance bottlenecks in PCI
+configuration space accesses, particularly in virtualization
+environments with high-density SR-IOV deployments where repeated
+enumeration of Virtual Functions creates substantial delays.
+
+What: /sys/bus/pci/pcsc/enabled
+Date: September 2025
+Contact: Linux PCI developers <linux-pci@...r.kernel.org>
+Description:
+ PCI Configuration Space Cache (PCSC) is a subsystem that
+ caches accesses to the PCI configuration space of PCI
+ functions. When this file contains the "1", the kernel
+ is utilizing the cache, while when on "0" the
+ system bypasses it. This setting can also be controlled
+parameter.
diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 747a55abf494..08c7a13f107c 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -5036,6 +5036,9 @@
pcmv= [HW,PCMCIA] BadgePAD 4
+ pcsc_enabled= [PCSC] enable the use of the PCI Configuration Space
+ Cache (PCSC).
+
pd_ignore_unused
[PM]
Keep all power-domains already enabled by bootloader on,
diff --git a/drivers/pci/pcsc.c b/drivers/pci/pcsc.c
index 343f8b03831a..44d842733230 100644
--- a/drivers/pci/pcsc.c
+++ b/drivers/pci/pcsc.c
@@ -16,13 +16,21 @@
#include <linux/atomic.h>
#include <linux/pcsc.h>
+#include <linux/sysfs.h>
+
+static bool pcsc_enabled;
+static int __init pcsc_enabled_setup(char *str)
+{
+ return kstrtobool(str, &pcsc_enabled) == 0;
+}
+__setup("pcsc_enabled=", pcsc_enabled_setup);
static bool pcsc_initialised;
static atomic_t num_nodes = ATOMIC_INIT(0);
inline bool pcsc_is_initialised(void)
{
- return pcsc_initialised;
+ return pcsc_initialised && pcsc_enabled;
}
static int pcsc_add_bus(struct pci_bus *bus)
@@ -899,14 +907,95 @@ static struct notifier_block pcsc_bus_nb = {
.notifier_call = pcsc_bus_notify,
};
+static ssize_t pcsc_enabled_show(struct kobject *kobj,
+ struct kobj_attribute *attr, char *buf)
+{
+ return sysfs_emit(buf, "%d\n", pcsc_enabled);
+}
+
+static ssize_t pcsc_enabled_store(struct kobject *kobj,
+ struct kobj_attribute *attr, const char *buf,
+ size_t count)
+{
+ bool new_value;
+ int ret;
+
+ ret = kstrtobool(buf, &new_value);
+ if (ret < 0)
+ return ret;
+
+ pcsc_enabled = new_value;
+ return count;
+}
+
+static struct kobj_attribute pcsc_enabled_attribute =
+ __ATTR(enabled, 0644, pcsc_enabled_show, pcsc_enabled_store);
+
+static struct attribute *pcsc_attrs[] = {
+ &pcsc_enabled_attribute.attr,
+ NULL,
+};
+
+static struct attribute_group pcsc_attr_group = {
+ .attrs = pcsc_attrs,
+};
+
+static struct kobject *pcsc_kobj;
+
+static void pcsc_create_sysfs(void)
+{
+ struct kset *pci_bus_kset;
+ int ret;
+
+ if (pcsc_kobj)
+ return; /* Already created */
+
+ pci_bus_kset = bus_get_kset(&pci_bus_type);
+ if (!pci_bus_kset) {
+ /* PCI bus kset not ready yet, will be retried later */
+ return;
+ }
+
+ pcsc_kobj = kobject_create_and_add("pcsc", &pci_bus_kset->kobj);
+ if (!pcsc_kobj) {
+ pr_err("Failed to create sysfs kobject\n");
+ return;
+ }
+
+ ret = sysfs_create_group(pcsc_kobj, &pcsc_attr_group);
+ if (ret) {
+ pr_err("Failed to create sysfs group\n");
+ kobject_put(pcsc_kobj);
+ pcsc_kobj = NULL;
+ return;
+ }
+}
+
static int __init pcsc_init(void)
{
bus_register_notifier(&pci_bus_type, &pcsc_bus_nb);
+ /* Try to create sysfs entry, but don't fail if PCI bus isn't ready yet */
+ pcsc_create_sysfs();
+
pcsc_initialised = true;
- pr_info("initialised\n");
+ pr_info("initialised (enabled=%d)\n", pcsc_enabled);
return 0;
}
+/* Late initcall to retry sysfs creation if it failed during core_initcall */
+static int __init pcsc_sysfs_init(void)
+{
+ pcsc_create_sysfs();
+ return 0;
+}
+
core_initcall(pcsc_init);
+
+/*
+ * The PCI subsystem is initialised later, therefore we need to add
+ * our sysfs entries later. This is done to avoid modifying the sysfs
+ * creation of the core pci driver.
+ */
+late_initcall(pcsc_sysfs_init);
--
2.47.3
Amazon Web Services Development Center Germany GmbH
Tamara-Danz-Str. 13
10243 Berlin
Geschaeftsfuehrung: Christian Schlaeger
Eingetragen am Amtsgericht Charlottenburg unter HRB 257764 B
Sitz: Berlin
Ust-ID: DE 365 538 597
Powered by blists - more mailing lists