PCI: Spread interrupt vectors in pci_alloc_irq_vectors()

Set the affinity_mask in the PCI device before allocating vectors so that
the affinity can be propagated through the MSI descriptor structures to the
core IRQ code.  To facilitate this, new __pci_enable_msi_range() and
__pci_enable_msix_range() helpers are factored out of their not prefixed
variants which assigning the new IRQ affinity mask in the PCI device so
that the low-level interrupt code can perform the interrupt affinity
assignment and do node-local allocations.

A new PCI_IRQ_NOAFFINITY flag is added to pci_alloc_irq_vectors() so that
this function can also be used by drivers that don't wish to use the
automatic affinity assignment.

[bhelgaas: omit "else" after "return" consistently]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Alexander Gordeev <agordeev@redhat.com>

3 files changed, 95 insertions, 45 deletions

diff --git a/Documentation/PCI/MSI-HOWTO.txt b/Documentation/PCI/MSI-HOWTO.txt
index 0ac612b8c3fb..c55df2911136 100644
--- a/Documentation/PCI/MSI-HOWTO.txt
+++ b/Documentation/PCI/MSI-HOWTO.txt
@@ -99,6 +99,10 @@ PCI_IRQ_NOMSI and PCI_IRQ_NOMSIX flag in case a device claims to support
 MSI or MSI-X, but the support is broken, or to pass PCI_IRQ_NOLEGACY in
 case the device does not support legacy interrupt lines.
 
+By default this function will spread the interrupts around the available
+CPUs, but this feature can be disabled by passing the PCI_IRQ_NOAFFINITY
+flag.
+
 To get the Linux IRQ numbers passed to request_irq() and free_irq() and the
 vectors, use the following function:
 
diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 5e5ab478ea7d..a02981efdad5 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -569,6 +569,7 @@ static struct msi_desc *msi_setup_entry(struct pci_dev *dev, int nvec)
         entry->msi_attrib.multi_cap     = (control & PCI_MSI_FLAGS_QMASK) >> 1;
         entry->msi_attrib.multiple      = ilog2(__roundup_pow_of_two(nvec));
         entry->nvec_used                = nvec;
+        entry->affinity                 = dev->irq_affinity;
 
         if (control & PCI_MSI_FLAGS_64BIT)
                 entry->mask_pos = dev->msi_cap + PCI_MSI_MASK_64;
@@ -680,10 +681,18 @@ static void __iomem *msix_map_region(struct pci_dev *dev, unsigned nr_entries)
 static int msix_setup_entries(struct pci_dev *dev, void __iomem *base,
                               struct msix_entry *entries, int nvec)
 {
+        const struct cpumask *mask = NULL;
         struct msi_desc *entry;
-        int i;
+        int cpu = -1, i;
 
         for (i = 0; i < nvec; i++) {
+                if (dev->irq_affinity) {
+                        cpu = cpumask_next(cpu, dev->irq_affinity);
+                        if (cpu >= nr_cpu_ids)
+                                cpu = cpumask_first(dev->irq_affinity);
+                        mask = cpumask_of(cpu);
+                }
+
                 entry = alloc_msi_entry(&dev->dev);
                 if (!entry) {
                         if (!i)
@@ -703,6 +712,7 @@ static int msix_setup_entries(struct pci_dev *dev, void __iomem *base,
                 entry->msi_attrib.default_irq   = dev->irq;
                 entry->mask_base                = base;
                 entry->nvec_used                = 1;
+                entry->affinity                 = mask;
 
                 list_add_tail(&entry->list, dev_to_msi_list(&dev->dev));
         }
@@ -1028,19 +1038,8 @@ int pci_msi_enabled(void)
 }
 EXPORT_SYMBOL(pci_msi_enabled);
 
-/**
- * pci_enable_msi_range - configure device's MSI capability structure
- * @dev: device to configure
- * @minvec: minimal number of interrupts to configure
- * @maxvec: maximum number of interrupts to configure
- *
- * This function tries to allocate a maximum possible number of interrupts in a
- * range between @minvec and @maxvec. It returns a negative errno if an error
- * occurs. If it succeeds, it returns the actual number of interrupts allocated
- * and updates the @dev's irq member to the lowest new interrupt number;
- * the other interrupt numbers allocated to this device are consecutive.
- **/
-int pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec)
+static int __pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec,
+                unsigned int flags)
 {
         int nvec;
         int rc;
@@ -1063,25 +1062,85 @@ int pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec)
         nvec = pci_msi_vec_count(dev);
         if (nvec < 0)
                 return nvec;
-        else if (nvec < minvec)
+        if (nvec < minvec)
                 return -EINVAL;
-        else if (nvec > maxvec)
+
+        if (nvec > maxvec)
                 nvec = maxvec;
 
-        do {
+        for (;;) {
+                if (!(flags & PCI_IRQ_NOAFFINITY)) {
+                        dev->irq_affinity = irq_create_affinity_mask(&nvec);
+                        if (nvec < minvec)
+                                return -ENOSPC;
+                }
+
                 rc = msi_capability_init(dev, nvec);
-                if (rc < 0) {
+                if (rc == 0)
+                        return nvec;
+
+                kfree(dev->irq_affinity);
+                dev->irq_affinity = NULL;
+
+                if (rc < 0)
                         return rc;
-                } else if (rc > 0) {
-                        if (rc < minvec)
+                if (rc < minvec)
+                        return -ENOSPC;
+
+                nvec = rc;
+        }
+}
+
+/**
+ * pci_enable_msi_range - configure device's MSI capability structure
+ * @dev: device to configure
+ * @minvec: minimal number of interrupts to configure
+ * @maxvec: maximum number of interrupts to configure
+ *
+ * This function tries to allocate a maximum possible number of interrupts in a
+ * range between @minvec and @maxvec. It returns a negative errno if an error
+ * occurs. If it succeeds, it returns the actual number of interrupts allocated
+ * and updates the @dev's irq member to the lowest new interrupt number;
+ * the other interrupt numbers allocated to this device are consecutive.
+ **/
+int pci_enable_msi_range(struct pci_dev *dev, int minvec, int maxvec)
+{
+        return __pci_enable_msi_range(dev, minvec, maxvec, PCI_IRQ_NOAFFINITY);
+}
+EXPORT_SYMBOL(pci_enable_msi_range);
+
+static int __pci_enable_msix_range(struct pci_dev *dev,
+                struct msix_entry *entries, int minvec, int maxvec,
+                unsigned int flags)
+{
+        int nvec = maxvec;
+        int rc;
+
+        if (maxvec < minvec)
+                return -ERANGE;
+
+        for (;;) {
+                if (!(flags & PCI_IRQ_NOAFFINITY)) {
+                        dev->irq_affinity = irq_create_affinity_mask(&nvec);
+                        if (nvec < minvec)
                                 return -ENOSPC;
-                        nvec = rc;
                 }
-        } while (rc);
 
-        return nvec;
+                rc = pci_enable_msix(dev, entries, nvec);
+                if (rc == 0)
+                        return nvec;
+
+                kfree(dev->irq_affinity);
+                dev->irq_affinity = NULL;
+
+                if (rc < 0)
+                        return rc;
+                if (rc < minvec)
+                        return -ENOSPC;
+
+                nvec = rc;
+        }
 }
-EXPORT_SYMBOL(pci_enable_msi_range);
 
 /**
  * pci_enable_msix_range - configure device's MSI-X capability structure
@@ -1099,26 +1158,10 @@ EXPORT_SYMBOL(pci_enable_msi_range);
  * with new allocated MSI-X interrupts.
  **/
 int pci_enable_msix_range(struct pci_dev *dev, struct msix_entry *entries,
-                               int minvec, int maxvec)
+                int minvec, int maxvec)
 {
-        int nvec = maxvec;
-        int rc;
-
-        if (maxvec < minvec)
-                return -ERANGE;
-
-        do {
-                rc = pci_enable_msix(dev, entries, nvec);
-                if (rc < 0) {
-                        return rc;
-                } else if (rc > 0) {
-                        if (rc < minvec)
-                                return -ENOSPC;
-                        nvec = rc;
-                }
-        } while (rc);
-
-        return nvec;
+        return __pci_enable_msix_range(dev, entries, minvec, maxvec,
+                        PCI_IRQ_NOAFFINITY);
 }
 EXPORT_SYMBOL(pci_enable_msix_range);
 
@@ -1145,13 +1188,14 @@ int pci_alloc_irq_vectors(struct pci_dev *dev, unsigned int min_vecs,
         int vecs = -ENOSPC;
 
         if (!(flags & PCI_IRQ_NOMSIX)) {
-                vecs = pci_enable_msix_range(dev, NULL, min_vecs, max_vecs);
+                vecs = __pci_enable_msix_range(dev, NULL, min_vecs, max_vecs,
+                                flags);
                 if (vecs > 0)
                         return vecs;
         }
 
         if (!(flags & PCI_IRQ_NOMSI)) {
-                vecs = pci_enable_msi_range(dev, min_vecs, max_vecs);
+                vecs = __pci_enable_msi_range(dev, min_vecs, max_vecs, flags);
                 if (vecs > 0)
                         return vecs;
         }
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 52ecd49e8049..f1406619f868 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -320,6 +320,7 @@ struct pci_dev {
          * directly, use the values stored here. They might be different!
          */
         unsigned int    irq;
+        struct cpumask  *irq_affinity;
         struct resource resource[DEVICE_COUNT_RESOURCE]; /* I/O and memory regions + expansion ROMs */
 
         bool match_driver;              /* Skip attaching driver */
@@ -1240,6 +1241,7 @@ int pci_set_vga_state(struct pci_dev *pdev, bool decode,
 #define PCI_IRQ_NOLEGACY        (1 << 0) /* don't use legacy interrupts */
 #define PCI_IRQ_NOMSI           (1 << 1) /* don't use MSI interrupts */
 #define PCI_IRQ_NOMSIX          (1 << 2) /* don't use MSI-X interrupts */
+#define PCI_IRQ_NOAFFINITY      (1 << 3) /* don't auto-assign affinity */
 
 /* kmem_cache style wrapper around pci_alloc_consistent() */