[PATCH kvmtool v3 0/3] vfio-pci: Support INTx mode re-enabling

[Leo Yan <leo.yan@linaro.org>]

When enable vfio-pci mode for NIC driver on Juno board, the IRQ is
failed to forward properly from host to guest, finally root caused this
issue is related with kvmtool cannot re-enable INTx mode properly.

So the basic working flow to reproduce this issue is as below:

    Host             Guest
-------------  --------------------
  INTx mode
                 MSI enable failed in NIC driver
                 MSI disable in NIC driver
                 Switch back to INTx mode --> kvmtool doesn't support

So this patch is to support INTx mode re-enabling; patch 0001 is one
minor fixing up for eventfd releasing; patch 0002 introduces a new
function vfio_pci_init_intx() which is used to finish INTx one-time
initialisation; patch 0003 is the core patch for support INTx mode
re-enabling, when kvmtool detects MSI is disabled it rollbacks to INTx
mode.

This patch set has been tested on Juno-r2 board.

== Changes for V3 ==
* Add new function vfio_pci_init_intx() for one-time initialisation.
* Simplized INTx re-enabling (don't change irq_line anymore at the
  runtime).


Leo Yan (3):
  vfio-pci: Release INTx's unmask eventfd properly
  vfio-pci: Add new function for INTx one-time initialisation
  vfio-pci: Re-enable INTx mode when disable MSI/MSIX

 include/kvm/vfio.h |   1 +
 vfio/pci.c         | 108 +++++++++++++++++++++++++++++----------------
 2 files changed, 72 insertions(+), 37 deletions(-)

-- 
2.19.1