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

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Date:	Fri, 3 Jun 2016 10:28:21 +0800
From:	Yongji Xie <xyjxie@...ux.vnet.ibm.com>
To:	Alex Williamson <alex.williamson@...hat.com>
Cc:	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	iommu@...ts.linux-foundation.org, bhelgaas@...gle.com,
	aik@...abs.ru, benh@...nel.crashing.org, paulus@...ba.org,
	mpe@...erman.id.au, joro@...tes.org, warrier@...ux.vnet.ibm.com,
	zhong@...ux.vnet.ibm.com, nikunj@...ux.vnet.ibm.com,
	eric.auger@...aro.org, will.deacon@....com,
	gwshan@...ux.vnet.ibm.com, alistair@...ple.id.au,
	ruscur@...sell.cc, kevin.tian@...el.com, David.Laight@...LAB.COM
Subject: Re: [RESEND PATCH v2 0/6] vfio-pci: Add support for mmapping MSI-X
 table

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,
>
> Alex

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.

Thanks,
Yongji

> On Thu,  2 Jun 2016 14:09:57 +0800
> Yongji Xie <xyjxie@...ux.vnet.ibm.com> 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
>>    in QEMU
>>
>> [1] https://www.mail-archive.com/linux-kernel%40vger.kernel.org/msg1138820.html
>>
>> Yongji Xie (6):
>>    PCI: Add a new PCI_BUS_FLAGS_MSI_REMAP flag
>>    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(-)
>>