[PATCH 4.12 72/99] virtio_pci: fix cpu affinity support

Greg Kroah-Hartman
2017-08-28T08:10:19Z

From: Christoph Hellwig <hch@lst.de>

commit ba74b6f7fcc07355d087af6939712eed4a454821 upstream.

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>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/virtio/virtio_pci_common.c | 10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)

--- a/drivers/virtio/virtio_pci_common.c
+++ b/drivers/virtio/virtio_pci_common.c
@@ -107,6 +107,7 @@ static int vp_request_msix_vectors(struc
{
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(struc
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;