[PATCH RFC 0/8] virtio: add guest MSI-X support

["Michael S. Tsirkin" <mst@redhat.com>]

Add optional MSI-X support: use a vector per virtqueue with
fallback to a common vector and finally to regular interrupt.
Teach all drivers to use it.

I added 2 new virtio operations: request_vqs/free_vqs because MSI
needs to know the total number of vectors upfront.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

---

Here's a draft set of patches for MSI-X support in the guest.  It still
needs to be tested properly, and performance impact measured, but I
thought I'd share it here in the hope of getting some very early
feedback/flames.

Michael S. Tsirkin (8):
  virtio: add request_vqs/free_vqs virtio operations
  virtio_blk: add request_vqs/free_vqs calls
  virtio-rng: add request_vqs/free_vqs calls
  virtio_console: add request_vqs/free_vqs calls
  virtio_net: add request_vqs/free_vqs calls
  virtio_balloon: add request_vqs/free_vqs calls
  virtio_pci: split up vp_interrupt
  virtio_pci: optional MSI-X support

 drivers/block/virtio_blk.c          |    9 ++-
 drivers/char/hw_random/virtio-rng.c |   10 ++-
 drivers/char/virtio_console.c       |    8 ++-
 drivers/net/virtio_net.c            |   16 +++-
 drivers/virtio/virtio_balloon.c     |    9 ++-
 drivers/virtio/virtio_pci.c         |  192 ++++++++++++++++++++++++++++++-----
 include/linux/virtio_config.h       |   35 +++++++
 7 files changed, 247 insertions(+), 32 deletions(-)