PCI/MSI: Return -ENOSPC from pci_alloc_irq_vectors_affinity()

The API of pci_alloc_irq_vectors_affinity() says it returns -ENOSPC if
fewer than @min_vecs interrupt vectors are available for @dev.

However, if a device supports MSI-X but not MSI and a caller requests
@min_vecs that can't be satisfied by MSI-X, we previously returned -EINVAL
(from the failed attempt to enable MSI), not -ENOSPC.

When -ENOSPC is returned, callers may reduce the number IRQs they request
and try again.  Most callers can use the @min_vecs and @max_vecs
parameters to avoid this retry loop, but that doesn't work when using IRQ
affinity "nr_sets" because rebalancing the sets is driver-specific.

This return value bug has been present since pci_alloc_irq_vectors() was
added in v4.10 by aff171641d18 ("PCI: Provide sensible IRQ vector
alloc/free routines"), but it wasn't an issue because @min_vecs/@max_vecs
removed the need for callers to iteratively reduce the number of IRQs
requested and retry the allocation, so they didn't need to distinguish
-ENOSPC from -EINVAL.

In v5.0, 6da4b3ab9a6e ("genirq/affinity: Add support for allocating
interrupt sets") added IRQ sets to the interface, which reintroduced the
need to check for -ENOSPC and possibly reduce the number of IRQs requested
and retry the allocation.

Signed-off-by: Ming Lei <ming.lei@redhat.com>
[bhelgaas: changelog]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Cc: Jens Axboe <axboe@fb.com>
Cc: Keith Busch <keith.busch@intel.com>
Cc: Christoph Hellwig <hch@lst.de>

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 7a1c8a09efa579595c3239aa562fba4a97fa8e56..4c0b47867258c554f91fd0b86e89d30630130b86 100644 (file)
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -1168,7 +1168,8 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
                                   const struct irq_affinity *affd)
 {
        static const struct irq_affinity msi_default_affd;
-       int vecs = -ENOSPC;
+       int msix_vecs = -ENOSPC;
+       int msi_vecs = -ENOSPC;
 
        if (flags & PCI_IRQ_AFFINITY) {
                if (!affd)
@@ -1179,16 +1180,17 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
        }
 
        if (flags & PCI_IRQ_MSIX) {
-               vecs = __pci_enable_msix_range(dev, NULL, min_vecs, max_vecs,
-                               affd);
-               if (vecs > 0)
-                       return vecs;
+               msix_vecs = __pci_enable_msix_range(dev, NULL, min_vecs,
+                                                   max_vecs, affd);
+               if (msix_vecs > 0)
+                       return msix_vecs;
        }
 
        if (flags & PCI_IRQ_MSI) {
-               vecs = __pci_enable_msi_range(dev, min_vecs, max_vecs, affd);
-               if (vecs > 0)
-                       return vecs;
+               msi_vecs = __pci_enable_msi_range(dev, min_vecs, max_vecs,
+                                                 affd);
+               if (msi_vecs > 0)
+                       return msi_vecs;
        }
 
        /* use legacy irq if allowed */
@@ -1199,7 +1201,9 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
                }
        }
 
-       return vecs;
+       if (msix_vecs == -ENOSPC)
+               return -ENOSPC;
+       return msi_vecs;
 }
 EXPORT_SYMBOL(pci_alloc_irq_vectors_affinity);