Re: [RFC PATCH v4 0/7] vfio-pci: Allow to mmap sub-page MMIO BARs and MSI-X table

From	Yongji Xie <xyjxie@linux.vnet.ibm.com>
Newsgroups	linux.kernel
Subject	Re: [RFC PATCH v4 0/7] vfio-pci: Allow to mmap sub-page MMIO BARs and MSI-X table
Date	2016-03-17 11:50 +0100
Message-ID	<rdDF7-6fy-1@gated-at.bofh.it> (permalink)
References	<r9Y5r-8lu-9@gated-at.bofh.it> <rdhlf-7Px-5@gated-at.bofh.it> <rdksO-1C9-11@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

On 2016/3/16 22:10, Bjorn Helgaas wrote:
> On Wed, Mar 16, 2016 at 06:51:56PM +0800, Yongji Xie wrote:
>> Ping.
> This is mainly VFIO stuff, and Alex had some security concerns, so I'm
> not going to spend much time looking at this until he's satisfied.
>
> When I do, I'll be looking hard at the resource_alignment kernel
> parameter.  I'm opposed to kernel parameters in general because
> they're very difficult for users to use correctly, and they lead to
> kernel code paths that are rarely tested and hard to maintain.  So
> I'll be looking for an excuse to reject changes in that area.
>
> The changelog for 2/7 says it "replaces IORESOURCE_STARTALIGN with
> IORESOURCE_WINDOW."  But even a glance at the patch itself shows that
> IORESOURCE_WINDOW is *added* to some places, and it doesn't *replace*
> IORESOURCE_STARTALIGN.

There is a problem with my statement. I mean we can use
IORESOURCE_WINDOW to identify bridge resources instead of
IORESOURCE_STARTALIGN here.

> The changelog for 4/7 says:
>
>    This is because vfio will not allow to passthrough one BAR's mmio
>    page which may be shared with other BARs.  To solve this performance
>    issue ...
>
> with no mention at all of the actual *reason* vfio doesn't allow that
> passthrough.  If I understand correctly, that reason has to do with
> security, so your justification must be much stronger than "solving a
> performance issue."

OK. I will try to make my justification become stronger.

Thanks,
Yongji Xie

Back to linux.kernel | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

[RFC PATCH v4 0/7] vfio-pci: Allow to mmap sub-page MMIO BARs and MSI-X table Yongji Xie <xyjxie@linux.vnet.ibm.com> - 2016-03-07 08:50 +0100
  [RFC PATCH v4 6/7] vfio-pci: Allow to mmap MSI-X table if IOMMU_CAP_INTR_REMAP was set Yongji Xie <xyjxie@linux.vnet.ibm.com> - 2016-03-07 09:00 +0100
    Re: [RFC PATCH v4 6/7] vfio-pci: Allow to mmap MSI-X table if  IOMMU_CAP_INTR_REMAP was set Alex Williamson <alex.williamson@redhat.com> - 2016-03-16 17:40 +0100
      Re: [RFC PATCH v4 6/7] vfio-pci: Allow to mmap MSI-X table if  IOMMU_CAP_INTR_REMAP was set Yongji Xie <xyjxie@linux.vnet.ibm.com> - 2016-03-17 12:40 +0100
  [RFC PATCH v4 5/7] vfio-pci: Allow to mmap sub-page MMIO BARs if the mmio page is exclusive Yongji Xie <xyjxie@linux.vnet.ibm.com> - 2016-03-07 09:00 +0100
    Re: [RFC PATCH v4 5/7] vfio-pci: Allow to mmap sub-page MMIO BARs  if the mmio page is exclusive Alex Williamson <alex.williamson@redhat.com> - 2016-03-16 17:40 +0100
      Re: [RFC PATCH v4 5/7] vfio-pci: Allow to mmap sub-page MMIO BARs if  the mmio page is exclusive Yongji Xie <xyjxie@linux.vnet.ibm.com> - 2016-03-17 12:40 +0100
  [RFC PATCH v4 4/7] PCI: Modify resource_alignment to support multiple devices Yongji Xie <xyjxie@linux.vnet.ibm.com> - 2016-03-07 09:00 +0100
    Re: [RFC PATCH v4 4/7] PCI: Modify resource_alignment to support  multiple devices Alex Williamson <alex.williamson@redhat.com> - 2016-03-16 17:40 +0100
      Re: [RFC PATCH v4 4/7] PCI: Modify resource_alignment to support  multiple devices Yongji Xie <xyjxie@linux.vnet.ibm.com> - 2016-03-17 12:30 +0100
        Re: [RFC PATCH v4 4/7] PCI: Modify resource_alignment to support  multiple devices Alex Williamson <alex.williamson@redhat.com> - 2016-03-17 13:50 +0100
          Re: [RFC PATCH v4 4/7] PCI: Modify resource_alignment to support  multiple devices Yongji Xie <xyjxie@linux.vnet.ibm.com> - 2016-03-18 16:10 +0100
  [RFC PATCH v4 3/7] PCI: Ignore resource_alignment if PCI_PROBE_ONLY was set Yongji Xie <xyjxie@linux.vnet.ibm.com> - 2016-03-07 09:00 +0100
    Re: [RFC PATCH v4 3/7] PCI: Ignore resource_alignment if  PCI_PROBE_ONLY was set Alex Williamson <alex.williamson@redhat.com> - 2016-03-16 17:40 +0100
      Re: [RFC PATCH v4 3/7] PCI: Ignore resource_alignment if  PCI_PROBE_ONLY was set Yongji Xie <xyjxie@linux.vnet.ibm.com> - 2016-03-17 12:40 +0100
  [RFC PATCH v4 7/7] powerpc/powernv/pci-ioda: Add IOMMU_CAP_INTR_REMAP for IODA host bridge Yongji Xie <xyjxie@linux.vnet.ibm.com> - 2016-03-07 09:00 +0100
    Re: [RFC PATCH v4 7/7] powerpc/powernv/pci-ioda: Add  IOMMU_CAP_INTR_REMAP for IODA host bridge Alex Williamson <alex.williamson@redhat.com> - 2016-03-16 17:40 +0100
      Re: [RFC PATCH v4 7/7] powerpc/powernv/pci-ioda: Add  IOMMU_CAP_INTR_REMAP for IODA host bridge Yongji Xie <xyjxie@linux.vnet.ibm.com> - 2016-03-17 12:40 +0100
        Re: [RFC PATCH v4 7/7] powerpc/powernv/pci-ioda: Add  IOMMU_CAP_INTR_REMAP for IODA host bridge Alex Williamson <alex.williamson@redhat.com> - 2016-03-17 13:50 +0100
          Re: [RFC PATCH v4 7/7] powerpc/powernv/pci-ioda: Add  IOMMU_CAP_INTR_REMAP for IODA host bridge Yongji Xie <xyjxie@linux.vnet.ibm.com> - 2016-03-18 13:00 +0100
  Re: [RFC PATCH v4 0/7] vfio-pci: Allow to mmap sub-page MMIO BARs and  MSI-X table Yongji Xie <xyjxie@linux.vnet.ibm.com> - 2016-03-16 12:00 +0100
    Re: [RFC PATCH v4 0/7] vfio-pci: Allow to mmap sub-page MMIO BARs  and MSI-X table Bjorn Helgaas <helgaas@kernel.org> - 2016-03-16 15:20 +0100
      Re: [RFC PATCH v4 0/7] vfio-pci: Allow to mmap sub-page MMIO BARs and  MSI-X table Yongji Xie <xyjxie@linux.vnet.ibm.com> - 2016-03-17 11:50 +0100

csiph-web