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

From: Yongji Xie
Date: Thu Jun 02 2016 - 22:28:43 EST

Hi, Alex

On 2016/6/2 21:11, Alex Williamson wrote:

AFAICT, you posted this *3* days ago, has something changed here or is
this just expedited nagging for review? This also depends on a
non-upstream series and crosses multiple functional areas, all of which
make it difficult for maintainers to actually do anything with this
series. Thanks,


I resend this series because I found the message-id of the previous email
is changed unexpectedly. The cover letter is not in the same thread as other
patches. It would be a little hard for people to review.


On Thu, 2 Jun 2016 14:09:57 +0800
Yongji Xie <xyjxie@xxxxxxxxxxxxxxxxxx> wrote:

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


Yongji Xie (6):
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(-)