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

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Date:   Mon, 14 Aug 2017 19:45:05 +1000
From:   Alexey Kardashevskiy <aik@...abs.ru>
To:     linuxppc-dev@...ts.ozlabs.org
Cc:     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: Re: [RFC PATCH v5 0/5] vfio-pci: Add support for mmapping MSI-X table

Folks,

Is there anything to change besides those compiler errors and David's
comment in 5/5? Or the while patchset is too bad? Thanks.



On 07/08/17 17:25, Alexey Kardashevskiy wrote:
> 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(-)
> 


-- 
Alexey