Groups > linux.kernel > #1242034

Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support

From	Gleb Natapov <gleb@scylladb.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support
Date	2015-10-08 10:00 +0200
Message-ID	<qhehl-5CS-21@gated-at.bofh.it> (permalink)
References	(5 earlier) <qgZV0-1TQ-27@gated-at.bofh.it> <qgZV0-1TQ-25@gated-at.bofh.it> <qh48i-884-29@gated-at.bofh.it> <qhaQp-Qf-3@gated-at.bofh.it> <qhe7E-5rB-9@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Thu, Oct 08, 2015 at 10:41:53AM +0300, Michael S. Tsirkin wrote:
> On Thu, Oct 08, 2015 at 07:19:13AM +0300, Gleb Natapov wrote:
> > Well
> > the alternative is to add /dev/vfio/nommu like you've said, but what
> > would be the difference between this and uio eludes me.
> 
> Are you familiar with vfio that you ask such a question?
> 
Yes, I do and I do not see anything of value that vfio can add to nommu
setup besides complexity, but I do see why it will have to have special
interface not applicable to regular vfio (hint: there is not HW to translate
virtual address to physical) and why it will have to be accessible to
root user only.

> Here's the vfio pci code:
> 
> $ wc -l drivers/vfio/pci/*
>    27 drivers/vfio/pci/Kconfig
>     4 drivers/vfio/pci/Makefile
>  1217 drivers/vfio/pci/vfio_pci.c
>  1602 drivers/vfio/pci/vfio_pci_config.c
>   675 drivers/vfio/pci/vfio_pci_intrs.c
>    92 drivers/vfio/pci/vfio_pci_private.h
>   238 drivers/vfio/pci/vfio_pci_rdwr.c
>  3855 total
>
> There's some code dealing with iommu groups in
> drivers/vfio/pci/vfio_pci.c,
> but most of it is validating input and
> presenting a consistent interface to userspace.
> 
What is has to do with the patch series in question? Non patched
uio_generic code does not validate input. If you think it should by all
means write the code (don't break existing use cases while doing so),
but the patch under discussion does not even access pci device from
userspace, so it will not be affected by said filtering.

> This is exactly what's missing here.
It is not missing in this patch series, it is missing from upstream
code. I do not remember this been an issue when uio_generic was accepted
into the kernel. The reason was because it meant to be accessible by root
only. VFIO was designed to be used by regular user from ground up, so
obviously unrestricted access to pci space was out of the question.
Different use cases lead to different designs, how surprising.

> 
> There's also drivers/vfio/virqfd.c which deals
> with sending interrupts over eventfds correctly.
> 
As opposite to this patch that deals with them incorrectly? In what way?

--
			Gleb.
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Thread

Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-06 16:40 +0200
  Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Vlad Zolotarov <vladz@cloudius-systems.com> - 2015-10-06 16:50 +0200
    Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-06 17:00 +0200
      Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Vlad Zolotarov <vladz@cloudius-systems.com> - 2015-10-06 17:30 +0200
      Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Avi Kivity <avi@scylladb.com> - 2015-10-06 17:30 +0200
        Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Alex Williamson <alex.williamson@redhat.com> - 2015-10-06 21:00 +0200
          Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Stephen Hemminger <stephen@networkplumber.org> - 2015-10-06 23:40 +0200
            Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Alex Williamson <alex.williamson@redhat.com> - 2015-10-06 23:50 +0200
              Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Vlad Zolotarov <vladz@cloudius-systems.com> - 2015-10-07 10:00 +0200
              Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Vlad Zolotarov <vladz@cloudius-systems.com> - 2015-10-07 10:10 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Vlad Zolotarov <vladz@cloudius-systems.com> - 2015-10-07 10:10 +0200
          Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Avi Kivity <avi@scylladb.com> - 2015-10-07 09:00 +0200
            Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Avi Kivity <avi@scylladb.com> - 2015-10-07 18:40 +0200
              Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-07 23:10 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Gleb Natapov <gleb@scylladb.com> - 2015-10-08 06:20 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 09:50 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Gleb Natapov <gleb@scylladb.com> - 2015-10-08 10:00 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 11:40 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Gleb Natapov <gleb@scylladb.com> - 2015-10-08 11:50 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 14:20 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Avi Kivity <avi@scylladb.com> - 2015-10-08 07:40 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 09:40 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Avi Kivity <avi@scylladb.com> - 2015-10-08 10:50 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 11:20 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Avi Kivity <avi@scylladb.com> - 2015-10-08 11:50 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 14:10 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Gleb Natapov <gleb@scylladb.com> - 2015-10-08 14:30 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 15:30 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Gleb Natapov <gleb@scylladb.com> - 2015-10-08 15:30 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 18:50 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Gleb Natapov <gleb@scylladb.com> - 2015-10-08 19:10 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 19:40 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Gleb Natapov <gleb@scylladb.com> - 2015-10-08 20:00 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Greg KH <gregkh@linuxfoundation.org> - 2015-10-08 20:40 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 10:40 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Gleb Natapov <gleb@scylladb.com> - 2015-10-08 11:00 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Avi Kivity <avi@scylladb.com> - 2015-10-08 11:20 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 12:30 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Avi Kivity <avi@scylladb.com> - 2015-10-08 15:30 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 16:20 +0200
                Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Alex Williamson <alex.williamson@redhat.com> - 2015-10-08 17:40 +0200
            Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Alex Williamson <alex.williamson@redhat.com> - 2015-10-07 18:40 +0200
              Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-07 22:10 +0200
          Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Vlad Zolotarov <vladz@cloudius-systems.com> - 2015-10-07 10:00 +0200
            Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support "Michael S. Tsirkin" <mst@redhat.com> - 2015-10-08 10:50 +0200

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