PCI/MSI: Forward MSI-X error code in pci_alloc_irq_vectors_affinity()

When debugging an issue where I was asking the PCI machinery to enable a
set of MSI-X vectors, without falling back on MSI, I ran across a behaviour
which seems odd. The pci_alloc_irq_vectors_affinity() will always return
-ENOSPC on failure, when allocating MSI-X vectors only, whereas with MSI
fallback it will forward any error returned by __pci_enable_msi_range().
This is a confusing behaviour, so have the pci_alloc_irq_vectors_affinity()
forward the error code from __pci_enable_msix_range() when appropriate.

Link: https://lore.kernel.org/r/20200616073318.20229-1-piotr.stankiewicz@intel.com
Signed-off-by: Piotr Stankiewicz <piotr.stankiewicz@intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@intel.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index 6b43a54..cade9be 100644 (file)
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -1191,8 +1191,7 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
                                   struct irq_affinity *affd)
 {
        struct irq_affinity msi_default_affd = {0};
-       int msix_vecs = -ENOSPC;
-       int msi_vecs = -ENOSPC;
+       int nvecs = -ENOSPC;
 
        if (flags & PCI_IRQ_AFFINITY) {
                if (!affd)
@@ -1203,17 +1202,16 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
        }
 
        if (flags & PCI_IRQ_MSIX) {
-               msix_vecs = __pci_enable_msix_range(dev, NULL, min_vecs,
-                                                   max_vecs, affd, flags);
-               if (msix_vecs > 0)
-                       return msix_vecs;
+               nvecs = __pci_enable_msix_range(dev, NULL, min_vecs, max_vecs,
+                                               affd, flags);
+               if (nvecs > 0)
+                       return nvecs;
        }
 
        if (flags & PCI_IRQ_MSI) {
-               msi_vecs = __pci_enable_msi_range(dev, min_vecs, max_vecs,
-                                                 affd);
-               if (msi_vecs > 0)
-                       return msi_vecs;
+               nvecs = __pci_enable_msi_range(dev, min_vecs, max_vecs, affd);
+               if (nvecs > 0)
+                       return nvecs;
        }
 
        /* use legacy IRQ if allowed */
@@ -1231,9 +1229,7 @@ int pci_alloc_irq_vectors_affinity(struct pci_dev *dev, unsigned int min_vecs,
                }
        }
 
-       if (msix_vecs == -ENOSPC)
-               return -ENOSPC;
-       return msi_vecs;
+       return nvecs;
 }
 EXPORT_SYMBOL(pci_alloc_irq_vectors_affinity);