[PATCH] sysfs: add per pci device msi[x] irq listing (v4)

Neil Horman
2011-09-29T14:39:05Z

This patch adds a per-pci-device subdirectory in sysfs called:
/sys/bus/pci/devices/<device>/msi_irqs

This sub-directory exports the set of msi vectors allocated by a given
pci device, by creating a numbered sub-directory for each vector beneath
msi_irqs. For each vector various attributes can be exported. Currently the
only attribute is called mode, which tracks the operational mode of that vector
(msi vs. msix)

---

Change Notes:

(v2)
Fixed up Documentation to put new sysfs interface descriptions in the right
place, as per request by Greg K-H

Fixed up oops that resulted from removing pci device. Not 100% sure I did this
exactly right, but looking at the crash (triggered by echo 1 >
/sys/class/net/eth0/device/remove), it looked as though we were freeing the
pci_dev struct prior to all sysfs objects releasing their use of the device. AS
such it seemed most appropriate to hold references on the pci_dev for each msi
irq sysfs object that we create, and release them on free accordingly. With
this change in place, I can remove, and add (via rescan) msi enabled devices
ad-nauseum without a panic. Again thanks to Greg K-H

(v3)
As per Gregs suggestion, I looked further and noted that in fact, yes, it wasn't
producing any errors on remove, but only because I had a refcounting problem,
and my new sysfs objects were left orphaned with a dangling refcount. I've
fixed that, added a release method to the new ktype, which now drops the
reference I hold on the pci_dev for us and I've validated that all objects I've
created, along with the parent directory and pci device are cleaned up and freed
by enabling the kobject dyanic_debug set and observing the appropriate release
calls. I can provide the logs if anyone wants to review them specifically.

(v4)
Fixed up some spelling mistakes, and added a scissors line with a good
commitlog, so that git-am drops all the version logging

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
CC: Greg Kroah-Hartman <gregkh@suse.de>
CC: Jesse Barnes <jbarnes@virtuousgeek.org>
CC: Bjorn Helgaas <bhelgaas@google.com>
CC: linux-pci@vger.kernel.org
---
Documentation/ABI/testing/sysfs-bus-pci | 18 +++++
drivers/pci/msi.c | 111 +++++++++++++++++++++++++++++++
include/linux/msi.h | 3 +
include/linux/pci.h | 1 +
4 files changed, 133 insertions(+), 0 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci
index 349ecf2..2e445b7 100644
--- a/Documentation/ABI/testing/sysfs-bus-pci
+++ b/Documentation/ABI/testing/sysfs-bus-pci
@@ -66,6 +66,24 @@ Description:
re-discover previously removed devices.
Depends on CONFIG_HOTPLUG.

+What: /sys/bus/pci/devices/.../msi_irqs/
+Date: September, 2011
+Contact: Neil Horman <nhorman@tuxdriver.com>
+Description:
+ The /sys/devices/.../msi_irqs directory contains a variable set
+ sub-directories, with each sub-directory being named after a
+ corresponding msi irq vector allocated to that device. Each
+ numbered sub-directory N contains attributes of that irq.
+ Note that this directory is not created for device drivers which
+ do not support msi irqs
+
+What: /sys/bus/pci/devices/.../msi_irqs/<N>/mode
+Date: September 2011
+Contact: Neil Horman <nhorman@tuxdriver.com>
+Description:
+ This attribute indicates the mode that the irq vector named by
+ the parent directory is in (msi vs. msix)
+
What: /sys/bus/pci/devices/.../remove
Date: January 2009
Contact: Linux PCI developers <linux-pci@vger.kernel.org>
diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 2f10328..73613e2 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -322,6 +322,8 @@ static void free_msi_irqs(struct pci_dev *dev)
if (list_is_last(&entry->list, &dev->msi_list))
iounmap(entry->mask_base);
}
+ kobject_del(&entry->kobj);
+ kobject_put(&entry->kobj);
list_del(&entry->list);
kfree(entry);
}
@@ -402,6 +404,98 @@ void pci_restore_msi_state(struct pci_dev *dev)
}
EXPORT_SYMBOL_GPL(pci_restore_msi_state);

+
+#define to_msi_attr(obj) container_of(obj, struct msi_attribute, attr)
+#define to_msi_desc(obj) container_of(obj, struct msi_desc, kobj)
+
+struct msi_attribute {
+ struct attribute attr;
+ ssize_t (*show)(struct msi_desc *entry, struct msi_attribute *attr,
+ char *buf);
+ ssize_t (*store)(struct msi_desc *entry, struct msi_attribute *attr,
+ const char *buf, size_t count);
+};
+
+static ssize_t show_msi_mode(struct msi_desc *entry, struct msi_attribute *atr,
+ char *buf)
+{
+ return sprintf(buf, "%s\n", entry->msi_attrib.is_msix ? "msix" : "msi");
+}
+
+static ssize_t msi_irq_attr_show(struct kobject *kobj,
+ struct attribute *attr, char *buf)
+{
+ struct msi_attribute *attribute = to_msi_attr(attr);
+ struct msi_desc *entry = to_msi_desc(kobj);
+
+ if (!attribute->show)
+ return -EIO;
+
+ return attribute->show(entry, attribute, buf);
+}
+
+static const struct sysfs_ops msi_irq_sysfs_ops = {
+ .show = msi_irq_attr_show,
+};
+
+static struct msi_attribute mode_attribute =
+ __ATTR(mode, S_IRUGO, show_msi_mode, NULL);
+
+
+struct attribute *msi_irq_default_attrs[] = {
+ &mode_attribute.attr,
+ NULL
+};
+
+void msi_kobj_release(struct kobject *kobj)
+{
+ struct msi_desc *entry = to_msi_desc(kobj);
+
+ pci_dev_put(entry->dev);
+}
+
+static struct kobj_type msi_irq_ktype = {
+ .release = msi_kobj_release,
+ .sysfs_ops = &msi_irq_sysfs_ops,
+ .default_attrs = msi_irq_default_attrs,
+};
+
+static int populate_msi_sysfs(struct pci_dev *pdev)
+{
+ struct msi_desc *entry;
+ struct kobject *kobj;
+ int ret;
+ int count = 0;
+
+ pdev->msi_kset = kset_create_and_add("msi_irqs", NULL, &pdev->dev.kobj);
+ if (!pdev->msi_kset)
+ return -ENOMEM;
+
+ list_for_each_entry(entry, &pdev->msi_list, list) {
+ kobj = &entry->kobj;
+ kobj->kset = pdev->msi_kset;
+ pci_dev_get(pdev);
+ ret = kobject_init_and_add(kobj, &msi_irq_ktype, NULL,
+ "%u", entry->irq);
+ if (ret)
+ goto out_unroll;
+
+ count++;
+ }
+
+ return 0;
+
+out_unroll:
+ list_for_each_entry(entry, &pdev->msi_list, list) {
+ if (!count)
+ break;
+ kobject_del(&entry->kobj);
+ kobject_put(&entry->kobj);
+ count--;
+ }
+ return ret;
+}
+
/**
* msi_capability_init - configure device's MSI capability structure
* @dev: pointer to the pci_dev data structure of MSI device function
@@ -453,6 +547,13 @@ static int msi_capability_init(struct pci_dev *dev, int nvec)
return ret;
}

+ ret = populate_msi_sysfs(dev);
+ if (ret) {
+ msi_mask_irq(entry, mask, ~mask);
+ free_msi_irqs(dev);
+ return ret;
+ }
+
/* Set MSI enabled bits */
pci_intx_for_msi(dev, 0);
msi_set_enable(dev, pos, 1);
@@ -573,6 +674,12 @@ static int msix_capability_init(struct pci_dev *dev,

msix_program_entries(dev, entries);

+ ret = populate_msi_sysfs(dev);
+ if (ret) {
+ ret = 0;
+ goto error;
+ }
+
/* Set MSI-X enabled bits and unmask the function */
pci_intx_for_msi(dev, 0);
dev->msix_enabled = 1;
@@ -731,6 +838,8 @@ void pci_disable_msi(struct pci_dev *dev)

pci_msi_shutdown(dev);
free_msi_irqs(dev);
+ kset_unregister(dev->msi_kset);
+ dev->msi_kset = NULL;
}
EXPORT_SYMBOL(pci_disable_msi);

@@ -829,6 +938,8 @@ void pci_disable_msix(struct pci_dev *dev)

pci_msix_shutdown(dev);
free_msi_irqs(dev);
+ kset_unregister(dev->msi_kset);
+ dev->msi_kset = NULL;
}
EXPORT_SYMBOL(pci_disable_msix);

diff --git a/include/linux/msi.h b/include/linux/msi.h
index 05acced..ce93a34 100644
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -1,6 +1,7 @@
#ifndef LINUX_MSI_H
#define LINUX_MSI_H

+#include <linux/kobject.h>
#include <linux/list.h>

struct msi_msg {
@@ -44,6 +45,8 @@ struct msi_desc {

/* Last set MSI message */
struct msi_msg msg;
+
+ struct kobject kobj;
};

/*
diff --git a/include/linux/pci.h b/include/linux/pci.h
index f27893b..fff3961 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -332,6 +332,7 @@ struct pci_dev {
struct bin_attribute *res_attr_wc[DEVICE_COUNT_RESOURCE]; /* sysfs file for WC mapping of resources */
#ifdef CONFIG_PCI_MSI
struct list_head msi_list;
+ struct kset *msi_kset;
#endif
struct pci_vpd *vpd;
#ifdef CONFIG_PCI_IOV
--
1.7.6.2