[PATCH V5 0/9] rework on the IRQ hardening of virtio

[Jason Wang <jasowang@redhat.com>]

Hi All:

This is a rework on the IRQ hardening for virtio which is done
previously by the following commits are reverted:

9e35276a5344 ("virtio_pci: harden MSI-X interrupts")
080cd7c3ac87 ("virtio-pci: harden INTX interrupts")

The reason is that it depends on the IRQF_NO_AUTOEN which may conflict
with the assumption of the affinity managed IRQ that is used by some
virtio drivers. And what's more, it is only done for virtio-pci but
not other transports.

In this rework, I try to implement a general virtio solution which
borrows the idea of the INTX hardening by re-using per virtqueue
boolean vq->broken and toggle it in virtio_device_ready() and
virtio_reset_device(). Then we can simply reuse the existing checks in
the vring_interrupt() and return early if the driver is not ready.

Note that, I only did compile test on ccw and MMIO transport.

Please review.

Changes since V4:

- use spin_lock_irq()/spin_unlock_irq() to synchronize with
  vring_interrupt() for ccw
- use spin_lock()/spin_unlock() to protect vring_interrupt() for non
  airq
- add comment to explain the ordering implications of set_status() for
  PCI, ccw and MMIO
- various tweaks on the comments and changelogs

Changes since V3:

- Rename synchornize_vqs() to synchronize_cbs()
- tweak the comment for synchronize_cbs()
- switch to use a dedicated helper __virtio_unbreak_device() and
  document it should be only used for probing
- switch to use rwlock to synchornize the non airq for ccw

Changes since V2:

- add ccw and MMIO support
- rename synchronize_vqs() to synchronize_cbs()
- switch to re-use vq->broken instead of introducing new device
  attributes for the future virtqueue reset support
  - remove unnecssary READ_ONCE()/WRITE_ONCE()
  - a new patch to remove device triggerable BUG_ON()
  - more tweaks on the comments

Changes since v1:

- Use transport specific irq synchronization method when possible
- Drop the module parameter and enable the hardening unconditonally
- Tweak the barrier/ordering facilities used in the code
- Reanme irq_soft_enabled to driver_ready
- Avoid unnecssary IRQ synchornization (e.g during boot)

Jason Wang (8):
  virtio: use virtio_reset_device() when possible
  virtio: introduce config op to synchronize vring callbacks
  virtio-pci: implement synchronize_cbs()
  virtio-mmio: implement synchronize_cbs()
  virtio-ccw: implement synchronize_cbs()
  virtio: allow to unbreak virtqueue
  virtio: harden vring IRQ
  virtio: use WARN_ON() to warning illegal status value

Stefano Garzarella (1):
  virtio: use virtio_device_ready() in virtio_device_restore()

 drivers/s390/virtio/virtio_ccw.c       | 31 +++++++++++++++++
 drivers/virtio/virtio.c                | 24 +++++++++----
 drivers/virtio/virtio_mmio.c           | 14 ++++++++
 drivers/virtio/virtio_pci_legacy.c     |  1 +
 drivers/virtio/virtio_pci_modern.c     |  2 ++
 drivers/virtio/virtio_pci_modern_dev.c |  5 +++
 drivers/virtio/virtio_ring.c           | 32 +++++++++++++++---
 include/linux/virtio.h                 |  1 +
 include/linux/virtio_config.h          | 47 +++++++++++++++++++++++++-
 9 files changed, 145 insertions(+), 12 deletions(-)

-- 
2.25.1