[patch 31/32] genirq/msi: Simplify sysfs handling

Thomas Gleixner
2021-11-27T01:33:37Z

The sysfs handling for MSI is a convoluted maze and it is in the way of
supporting dynamic expansion of the MSI-X vectors because it only supports
a one off bulk population/free of the sysfs entries.

Change it to do:

1) Creating an empty sysfs attribute group when msi_device_data is
allocated

2) Populate the entries when the MSI descriptor is initialized

3) Free the entries when a MSI descriptor is detached from a Linux
interrupt.

4) Provide functions for the legacy non-irqdomain fallback code to
do a bulk population/free. This code won't support dynamic
expansion.

This makes the code simpler and reduces the number of allocations as the
empty attribute group can be shared.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
include/linux/msi.h | 7 +
kernel/irq/msi.c | 196 +++++++++++++++++++++++-----------------------------
2 files changed, 95 insertions(+), 108 deletions(-)

--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -72,6 +72,7 @@ struct irq_data;
struct msi_desc;
struct pci_dev;
struct platform_msi_priv_data;
+struct device_attribute;

void __get_cached_msi_msg(struct msi_desc *entry, struct msi_msg *msg);
#ifdef CONFIG_GENERIC_MSI_IRQ
@@ -127,6 +128,7 @@ struct pci_msi_desc {
* @dev: Pointer to the device which uses this descriptor
* @msg: The last set MSI message cached for reuse
* @affinity: Optional pointer to a cpu affinity mask for this descriptor
+ * @sysfs_attr: Pointer to sysfs device attribute
*
* @write_msi_msg: Callback that may be called when the MSI message
* address or data changes
@@ -146,6 +148,9 @@ struct msi_desc {
#ifdef CONFIG_IRQ_MSI_IOMMU
const void *iommu_cookie;
#endif
+#ifdef CONFIG_SYSFS
+ struct device_attribute *sysfs_attrs;
+#endif

void (*write_msi_msg)(struct msi_desc *entry, void *data);
void *write_msi_msg_data;
@@ -171,7 +176,6 @@ enum msi_desc_filter {
* @lock: Spinlock to protect register access
* @properties: MSI properties which are interesting to drivers
* @num_descs: The number of allocated MSI descriptors for the device
- * @attrs: Pointer to the sysfs attribute group
* @platform_data: Platform-MSI specific data
* @list: List of MSI descriptors associated to the device
* @mutex: Mutex protecting the MSI list
@@ -182,7 +186,6 @@ struct msi_device_data {
raw_spinlock_t lock;
unsigned long properties;
unsigned int num_descs;
- const struct attribute_group **attrs;
struct platform_msi_priv_data *platform_data;
struct list_head list;
struct mutex mutex;
--- a/kernel/irq/msi.c
+++ b/kernel/irq/msi.c
@@ -19,6 +19,7 @@

#include "internals.h"

+static inline int msi_sysfs_create_group(struct device *dev);
#define dev_to_msi_list(dev) (&(dev)->msi.data->list)

/**
@@ -208,6 +209,7 @@ static void msi_device_data_release(stru
int msi_setup_device_data(struct device *dev)
{
struct msi_device_data *md;
+ int ret;

if (dev->msi.data)
return 0;
@@ -216,6 +218,12 @@ int msi_setup_device_data(struct device
if (!md)
return -ENOMEM;

+ ret = msi_sysfs_create_group(dev);
+ if (ret) {
+ devres_free(md);
+ return ret;
+ }
+
raw_spin_lock_init(&md->lock);
INIT_LIST_HEAD(&md->list);
mutex_init(&md->mutex);
@@ -395,6 +403,20 @@ int __msi_get_virq(struct device *dev, u
EXPORT_SYMBOL_GPL(__msi_get_virq);

#ifdef CONFIG_SYSFS
+static struct attribute *msi_dev_attrs[] = {
+ NULL
+};
+
+static const struct attribute_group msi_irqs_group = {
+ .name = "msi_irqs",
+ .attrs = msi_dev_attrs,
+};
+
+static inline int msi_sysfs_create_group(struct device *dev)
+{
+ return devm_device_add_group(dev, &msi_irqs_group);
+}
+
static ssize_t msi_mode_show(struct device *dev, struct device_attribute *attr,
char *buf)
{
@@ -404,97 +426,74 @@ static ssize_t msi_mode_show(struct devi
return sysfs_emit(buf, "%s\n", is_msix ? "msix" : "msi");
}

-/**
- * msi_populate_sysfs - Populate msi_irqs sysfs entries for devices
- * @dev: The device(PCI, platform etc) who will get sysfs entries
- */
-static const struct attribute_group **msi_populate_sysfs(struct device *dev)
+static void msi_sysfs_remove_desc(struct device *dev, struct msi_desc *desc)
{
- const struct attribute_group **msi_irq_groups;
- struct attribute **msi_attrs, *msi_attr;
- struct device_attribute *msi_dev_attr;
- struct attribute_group *msi_irq_group;
- struct msi_desc *entry;
- int ret = -ENOMEM;
- int num_msi = 0;
- int count = 0;
+ struct device_attribute *attrs = desc->sysfs_attrs;
int i;

- /* Determine how many msi entries we have */
- msi_for_each_desc(entry, dev, MSI_DESC_ALL)
- num_msi += entry->nvec_used;
- if (!num_msi)
- return NULL;
+ if (!attrs)
+ return;

- /* Dynamically create the MSI attributes for the device */
- msi_attrs = kcalloc(num_msi + 1, sizeof(void *), GFP_KERNEL);
- if (!msi_attrs)
- return ERR_PTR(-ENOMEM);
-
- msi_for_each_desc(entry, dev, MSI_DESC_ALL) {
- for (i = 0; i < entry->nvec_used; i++) {
- msi_dev_attr = kzalloc(sizeof(*msi_dev_attr), GFP_KERNEL);
- if (!msi_dev_attr)
- goto error_attrs;
- msi_attrs[count] = &msi_dev_attr->attr;
-
- sysfs_attr_init(&msi_dev_attr->attr);
- msi_dev_attr->attr.name = kasprintf(GFP_KERNEL, "%d",
- entry->irq + i);
- if (!msi_dev_attr->attr.name)
- goto error_attrs;
- msi_dev_attr->attr.mode = 0444;
- msi_dev_attr->show = msi_mode_show;
- ++count;
- }
+ desc->sysfs_attrs = NULL;
+ for (i = 0; i < desc->nvec_used; i++) {
+ if (attrs[i].show)
+ sysfs_remove_file_from_group(&dev->kobj, &attrs[i].attr, msi_irqs_group.name);
+ kfree(attrs[i].attr.name);
}
+ kfree(attrs);
+}

- msi_irq_group = kzalloc(sizeof(*msi_irq_group), GFP_KERNEL);
- if (!msi_irq_group)
- goto error_attrs;
- msi_irq_group->name = "msi_irqs";
- msi_irq_group->attrs = msi_attrs;
-
- msi_irq_groups = kcalloc(2, sizeof(void *), GFP_KERNEL);
- if (!msi_irq_groups)
- goto error_irq_group;
- msi_irq_groups[0] = msi_irq_group;
+static int msi_sysfs_populate_desc(struct device *dev, struct msi_desc *desc)
+{
+ struct device_attribute *attrs;
+ int ret, i;

- ret = sysfs_create_groups(&dev->kobj, msi_irq_groups);
- if (ret)
- goto error_irq_groups;
+ attrs = kcalloc(desc->nvec_used, sizeof(*attrs), GFP_KERNEL);
+ if (!attrs)
+ return -ENOMEM;
+
+ desc->sysfs_attrs = attrs;
+ for (i = 0; i < desc->nvec_used; i++) {
+ sysfs_attr_init(&attrs[i].attr);
+ attrs[i].attr.name = kasprintf(GFP_KERNEL, "%d", desc->irq + i);
+ if (!attrs[i].attr.name) {
+ ret = -ENOMEM;
+ goto fail;
+ }

- return msi_irq_groups;
+ attrs[i].attr.mode = 0444;
+ attrs[i].show = msi_mode_show;

-error_irq_groups:
- kfree(msi_irq_groups);
-error_irq_group:
- kfree(msi_irq_group);
-error_attrs:
- count = 0;
- msi_attr = msi_attrs[count];
- while (msi_attr) {
- msi_dev_attr = container_of(msi_attr, struct device_attribute, attr);
- kfree(msi_attr->name);
- kfree(msi_dev_attr);
- ++count;
- msi_attr = msi_attrs[count];
+ ret = sysfs_add_file_to_group(&dev->kobj, &attrs[i].attr, msi_irqs_group.name);
+ if (ret) {
+ attrs[i].show = NULL;
+ goto fail;
+ }
}
- kfree(msi_attrs);
- return ERR_PTR(ret);
+ return 0;
+
+fail:
+ msi_sysfs_remove_desc(dev, desc);
+ return ret;
}

+#ifdef CONFIG_PCI_MSI_ARCH_FALLBACK
/**
* msi_device_populate_sysfs - Populate msi_irqs sysfs entries for a device
* @dev: The device(PCI, platform etc) which will get sysfs entries
*/
int msi_device_populate_sysfs(struct device *dev)
{
- const struct attribute_group **group = msi_populate_sysfs(dev);
+ struct msi_desc *desc;
+ int ret;

- if (IS_ERR(group))
- return PTR_ERR(group);
- dev->msi.data->attrs = group;
+ msi_for_each_desc(desc, dev, MSI_DESC_ASSOCIATED) {
+ if (desc->sysfs_attrs)
+ continue;
+ ret = msi_sysfs_populate_desc(dev, desc);
+ if (ret)
+ return ret;
+ }
return 0;
}

@@ -505,28 +504,17 @@ int msi_device_populate_sysfs(struct dev
*/
void msi_device_destroy_sysfs(struct device *dev)
{
- const struct attribute_group **msi_irq_groups = dev->msi.data->attrs;
- struct device_attribute *dev_attr;
- struct attribute **msi_attrs;
- int count = 0;
-
- dev->msi.data->attrs = NULL;
- if (!msi_irq_groups)
- return;
+ struct msi_desc *desc;

- sysfs_remove_groups(&dev->kobj, msi_irq_groups);
- msi_attrs = msi_irq_groups[0]->attrs;
- while (msi_attrs[count]) {
- dev_attr = container_of(msi_attrs[count], struct device_attribute, attr);
- kfree(dev_attr->attr.name);
- kfree(dev_attr);
- ++count;
- }
- kfree(msi_attrs);
- kfree(msi_irq_groups[0]);
- kfree(msi_irq_groups);
+ msi_for_each_desc(desc, dev, MSI_DESC_ALL)
+ msi_sysfs_remove_desc(dev, desc);
}
-#endif
+#endif /* CONFIG_PCI_MSI_ARCH_FALLBACK */
+#else /* CONFIG_SYSFS */
+static inline int msi_sysfs_create_group(struct device *dev) { return 0; }
+static inline int msi_sysfs_populate_desc(struct device *dev, struct msi_desc *desc) { return 0; }
+static inline void msi_sysfs_remove_desc(struct device *dev, struct msi_desc *desc) { }
+#endif /* !CONFIG_SYSFS */

#ifdef CONFIG_GENERIC_MSI_IRQ_DOMAIN
static inline void irq_chip_write_msi_msg(struct irq_data *data,
@@ -959,6 +947,12 @@ int __msi_domain_alloc_irqs(struct irq_d
ret = msi_init_virq(domain, virq + i, vflags);
if (ret)
return ret;
+
+ if (info->flags & MSI_FLAG_DEV_SYSFS) {
+ ret = msi_sysfs_populate_desc(dev, desc);
+ if (ret)
+ return ret;
+ }
}
allocated++;
}
@@ -1003,18 +997,7 @@ int msi_domain_alloc_irqs_descs_locked(s

ret = ops->domain_alloc_irqs(domain, dev, nvec);
if (ret)
- goto cleanup;
-
- if (!(info->flags & MSI_FLAG_DEV_SYSFS))
- return 0;
-
- ret = msi_device_populate_sysfs(dev);
- if (ret)
- goto cleanup;
- return 0;
-
-cleanup:
- msi_domain_free_irqs_descs_locked(domain, dev);
+ msi_domain_free_irqs_descs_locked(domain, dev);
return ret;
}

@@ -1039,6 +1022,7 @@ int msi_domain_alloc_irqs(struct irq_dom

void __msi_domain_free_irqs(struct irq_domain *domain, struct device *dev)
{
+ struct msi_domain_info *info = domain->host_data;
struct irq_data *irqd;
struct msi_desc *desc;
int i;
@@ -1053,6 +1037,8 @@ void __msi_domain_free_irqs(struct irq_d
}

irq_domain_free_irqs(desc->irq, desc->nvec_used);
+ if (info->flags & MSI_FLAG_DEV_SYSFS)
+ msi_sysfs_remove_desc(dev, desc);
desc->irq = 0;
}
}
@@ -1081,8 +1067,6 @@ void msi_domain_free_irqs_descs_locked(s

lockdep_assert_held(&dev->msi.data->mutex);

- if (info->flags & MSI_FLAG_DEV_SYSFS)
- msi_device_destroy_sysfs(dev);
ops->domain_free_irqs(domain, dev);
msi_domain_free_msi_descs(info, dev);
}