• Ming Lei's avatar
    PCI/MSI: Return -ENOSPC from pci_alloc_irq_vectors_affinity() · 77f88abd
    Ming Lei authored
    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 aff17164 ("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, 6da4b3ab
    
     ("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: default avatarMing Lei <ming.lei@redhat.com>
    [bhelgaas: changelog]
    Signed-off-by: default avatarBjorn Helgaas <bhelgaas@google.com>
    Cc: Jens Axboe <axboe@fb.com>
    Cc: Keith Busch <keith.busch@intel.com>
    Cc: Christoph Hellwig <hch@lst.de>
    77f88abd