[PATCH v2 0/6] vfio-pci: Add support for mmapping MSI-X table

[Yongji Xie <xyjxie@linux.vnet.ibm.com>]

Current vfio-pci implementation disallows to mmap the page
containing MSI-X table in case that users can write directly
to MSI-X table and generate an incorrect MSIs.

However, this will cause some performance issue when there
are some critical device registers in the same page as the 
MSI-X table. We have to handle the mmio access to these
registers in QEMU emulation rather than in guest.

To solve this issue, this series allows to expose MSI-X table
to userspace when hardware enables the capability of interrupt
remapping which can ensure that a given PCI device can only
shoot the MSIs assigned for it. And we introduce a new bus_flags
PCI_BUS_FLAGS_MSI_REMAP to test this capability on PCI side
for different archs.

The patch 3 are based on the proposed patchset[1].

Changelog v2: 
- Make the commit log more clear
- Replace pci_bus_check_msi_remapping() with pci_bus_msi_isolated()
  so that we could clearly know what the function does
- Set PCI_BUS_FLAGS_MSI_REMAP in pci_create_root_bus() instead
  of iommu_bus_notifier()
- Reserve VFIO_REGION_INFO_FLAG_CAPS when we allow to mmap MSI-X
  table so that we can know whether we allow to mmap MSI-X table
  in QEMU

[1] https://www.mail-archive.com/linux-kernel%40vger.kernel.org/msg1138820.html

Yongji Xie (6):
  PCI: Add a new PCI_BUS_FLAGS_MSI_REMAP flag
  PCI: Set PCI_BUS_FLAGS_MSI_REMAP if MSI controller enables IRQ remapping
  PCI: Set PCI_BUS_FLAGS_MSI_REMAP if IOMMU have capability of IRQ remapping
  iommu: Set PCI_BUS_FLAGS_MSI_REMAP on iommu driver initialization
  pci-ioda: Set PCI_BUS_FLAGS_MSI_REMAP for IODA host bridge
  vfio-pci: Allow to expose MSI-X table to userspace if interrupt remapping is enabled

 arch/powerpc/platforms/powernv/pci-ioda.c |    8 ++++++++
 drivers/iommu/iommu.c                     |    8 ++++++++
 drivers/pci/msi.c                         |   15 +++++++++++++++
 drivers/pci/probe.c                       |    7 +++++++
 drivers/vfio/pci/vfio_pci.c               |   17 ++++++++++++++---
 drivers/vfio/pci/vfio_pci_rdwr.c          |    3 ++-
 include/linux/msi.h                       |    5 ++++-
 include/linux/pci.h                       |    1 +
 8 files changed, 59 insertions(+), 5 deletions(-)

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1.7.9.5