linux-kernel - Re: [PATCH kernel 0/3] vfio-pci: Add support for mmapping MSI-X table

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Date:   Thu, 15 Jun 2017 15:44:04 +1000
From:   Alexey Kardashevskiy <aik@...abs.ru>
To:     linuxppc-dev@...ts.ozlabs.org
Cc:     kvm@...r.kernel.org, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org, Yongji Xie <elohimes@...il.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Gavin Shan <gwshan@...ux.vnet.ibm.com>,
        Paul Mackerras <paulus@...ba.org>,
        David Gibson <david@...son.dropbear.id.au>
Subject: Re: [PATCH kernel 0/3] vfio-pci: Add support for mmapping MSI-X table

Ouch, this is a wrong one, please ignore. I'll repost in a sec.


On 15/06/17 15:06, Alexey Kardashevskiy wrote:
> Here is a patchset which Yongji was working on before
> leaving IBM LTC. Since we still want to have this functionality
> in the kernel (DPDK is the first user), here is a rebase
> on the current upstream.
> 
> 
> 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
> v3:
> - rebased on the current upstream
> 
> 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
> 
> 
> This is based on sha1
> 63f700aab4c1 Linus Torvalds "Merge tag 'xtensa-20170612' of git://github.com/jcmvbkbc/linux-xtensa".
> 
> Please comment. Thanks.
> 
> 
> 
> Yongji Xie (3):
>   PCI: Add a new PCI_BUS_FLAGS_MSI_REMAP flag
>   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
> 
>  include/linux/pci.h                       |  1 +
>  arch/powerpc/platforms/powernv/pci-ioda.c |  8 ++++++++
>  drivers/vfio/pci/vfio_pci.c               | 18 +++++++++++++++---
>  drivers/vfio/pci/vfio_pci_rdwr.c          |  3 ++-
>  4 files changed, 26 insertions(+), 4 deletions(-)
> 


-- 
Alexey