virtio_pci: fix cpu affinity support

Commit 0b0f9dc5 ("Revert "virtio_pci: use shared interrupts for
virtqueues"") removed the adjustment of the pre_vectors for the virtio
MSI-X vector allocation which was added in commit fb5e31d9 ("virtio:
allow drivers to request IRQ affinity when creating VQs"). This will
lead to an incorrect assignment of MSI-X vectors, and potential
deadlocks when offlining cpus.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Fixes: 0b0f9dc5 ("Revert "virtio_pci: use shared interrupts for virtqueues")
Reported-by: YASUAKI ISHIMATSU <yasu.isimatu@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
index 007a4f3660862e1aa6e9a16207ae54bbbab61d58..1c4797e53f686b03323e4316d443c256854268dc 100644 (file)
--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -107,6 +107,7 @@ static int vp_request_msix_vectors(struct virtio_device *vdev, int nvectors,
 {
        struct virtio_pci_device *vp_dev = to_vp_device(vdev);
        const char *name = dev_name(&vp_dev->vdev.dev);
+       unsigned flags = PCI_IRQ_MSIX;
        unsigned i, v;
        int err = -ENOMEM;
 
@@ -126,10 +127,13 @@ static int vp_request_msix_vectors(struct virtio_device *vdev, int nvectors,
                                        GFP_KERNEL))
                        goto error;
 
+       if (desc) {
+               flags |= PCI_IRQ_AFFINITY;
+               desc->pre_vectors++; /* virtio config vector */
+       }
+
        err = pci_alloc_irq_vectors_affinity(vp_dev->pci_dev, nvectors,
-                                            nvectors, PCI_IRQ_MSIX |
-                                            (desc ? PCI_IRQ_AFFINITY : 0),
-                                            desc);
+                                            nvectors, flags, desc);
        if (err < 0)
                goto error;
        vp_dev->msix_enabled = 1;