linux-kernel - [RFC PATCH v5 0/5] vfio-pci: Add support for mmapping MSI-X table

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Date:   Mon,  7 Aug 2017 17:25:43 +1000
From:   Alexey Kardashevskiy <aik@...abs.ru>
To:     linuxppc-dev@...ts.ozlabs.org
Cc:     Alexey Kardashevskiy <aik@...abs.ru>,
        David Gibson <david@...son.dropbear.id.au>,
        kvm-ppc@...r.kernel.org, kvm@...r.kernel.org,
        Yongji Xie <elohimes@...il.com>,
        Eric Auger <eric.auger@...hat.com>,
        Kyle Mahlkuch <Kyle.Mahlkuch@....com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Jike Song <jike.song@...el.com>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        Arvind Yadav <arvind.yadav.cs@...il.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Kirti Wankhede <kwankhede@...dia.com>,
        Mauricio Faria de Oliveira <mauricfo@...ux.vnet.ibm.com>,
        Neo Jia <cjia@...dia.com>, Paul Mackerras <paulus@...ba.org>,
        Vlad Tsyrklevich <vlad@...rklevich.net>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH v5 0/5] vfio-pci: Add support for mmapping MSI-X table


This is a followup for "[PATCH kernel v4 0/6] vfio-pci: Add support for mmapping MSI-X table"
http://www.spinics.net/lists/kvm/msg152232.html

This time it is using "caps" in IOMMU groups. The main question is if PCI
bus flags or IOMMU domains are still better (and which one).



Here is some background:

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.


This is based on sha1
26c5cebfdb6c "Merge branch 'parisc-4.13-4' of git://git.kernel.org/pub/scm/linux/kernel/git/deller/parisc-linux"

Please comment. Thanks.

Changelog:

v5:
* redid the whole thing via so-called IOMMU group capabilities

v4:
* rebased on recent upstream
* got all 6 patches from v2 (v3 was missing some)




Alexey Kardashevskiy (5):
  iommu: Add capabilities to a group
  iommu: Set IOMMU_GROUP_CAP_ISOLATE_MSIX if MSI controller enables IRQ
    remapping
  iommu/intel/amd: Set IOMMU_GROUP_CAP_ISOLATE_MSIX if IRQ remapping is
    enabled
  powerpc/iommu: Set IOMMU_GROUP_CAP_ISOLATE_MSIX
  vfio-pci: Allow to expose MSI-X table to userspace when safe

 include/linux/iommu.h            | 20 ++++++++++++++++++++
 include/linux/vfio.h             |  1 +
 arch/powerpc/kernel/iommu.c      |  1 +
 drivers/iommu/amd_iommu.c        |  3 +++
 drivers/iommu/intel-iommu.c      |  3 +++
 drivers/iommu/iommu.c            | 35 +++++++++++++++++++++++++++++++++++
 drivers/vfio/pci/vfio_pci.c      | 20 +++++++++++++++++---
 drivers/vfio/pci/vfio_pci_rdwr.c |  5 ++++-
 drivers/vfio/vfio.c              | 15 +++++++++++++++
 9 files changed, 99 insertions(+), 4 deletions(-)

-- 
2.11.0