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

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Date:   Mon, 21 Aug 2017 12:47:57 +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,

Ok, people did talk, exchanged ideas, lovely :) What happens now? Do I
repost this or go back to PCI bus flags or something else? Thanks.



On 14/08/17 19:45, Alexey Kardashevskiy wrote:
> 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