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>

1 files changed, 7 insertions, 3 deletions

diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
index 007a4f366086..1c4797e53f68 100644
--- 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;