On Wed, Mar 01, 2017 at 04:02:53PM +0100, Viktor Mihajlovski wrote:

On 01.03.2017 04:30, Zbigniew Jędrzejewski-Szmek wrote:

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On Tue, Feb 28, 2017 at 09:47:42AM +0100, Viktor Mihajlovski wrote:

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One could argue about back-level compatibility, but virtio by-path
naming has changed multiple times. We have seen virtio-pci-virtio<n>
(not predictable), pci-<busid> and virtio-pci-<busid> already. It
might be a good time now to settle on a common approach for all
virtio types.

For the reasons above, I'd vote for <subsystem>-<busid>, which
would work for PCI and CCW, not sure about ARM MMIO though.

It seems that there's agreement that <subsystem>-<busid> is the right
approach.

Ideally we would keep the virtio-pci-<busid> links as they appear
right now, for backwards compatibility, just for the pci devices, and
mark them as deprecated (dunno where, maybe just in NEWS), and add the
code to make the links.

I haven't looked at the code, maybe we just do this with the right
udev rule, and also stick the deprecation comment there?

Zbyszek

I've posted a github pull request [1], and would appreciate review
feedback. As I am lacking an ARM setup, it would also be nice if someone
with ARM skills could have a look as well.

FYI you can install ARM7 guests on an x86_64 host, using pre-built Fedora
images

  https://fedoraproject.org/wiki/QA:Testcase_Virt_ARM_on_x86

NB, this will install the guest using virtio-pci. So if you want to
see virtio-mmio in action, you'll need to edit the libvirt XML config
afterwards to add another disk, eg

    <disk type='file' device='disk'>
      <driver name='qemu' type='qcow2'/>
      <source file='/var/lib/libvirt/images/data.qcow2'/>
      <target dev='vda' bus='virtio'/>
      <address type='virtio-mmio'/>
    </disk>

If wanted, I can take a stab at virtio-mmio, but would need the output
of udevadm -a /dev/vda from a virtio-mmio system.

Presumably you mean 'udevadm info -a /dev/vda' ?  That reports the following,
given a basic Fedora 25 guest, with a virtio-mmio disk added as per the
guide above...

  looking at device '/devices/platform/a003e00.virtio_mmio/virtio3/block/vda':
    KERNEL=="vda"
    SUBSYSTEM=="block"
    DRIVER==""
    ATTR{alignment_offset}=="0"
    ATTR{badblocks}==""
    ATTR{cache_type}=="write back"
    ATTR{capability}=="50"
    ATTR{discard_alignment}=="0"
    ATTR{ext_range}=="256"
    ATTR{inflight}=="       0        0"
    ATTR{range}=="16"
    ATTR{removable}=="0"
    ATTR{ro}=="0"
    ATTR{serial}==""
    ATTR{size}=="2097152"
    ATTR{stat}=="      94        0     4208      285        0        0        0 
       0        0      100      280"

  looking at parent device '/devices/platform/a003e00.virtio_mmio/virtio3':
    KERNELS=="virtio3"
    SUBSYSTEMS=="virtio"
    DRIVERS=="virtio_blk"
    ATTRS{device}=="0x0002"
    ATTRS{features}=="0010101101110000000000000000110000000000000000000000000000
000000"
    ATTRS{status}=="0x00000007"
    ATTRS{vendor}=="0x554d4551"

  looking at parent device '/devices/platform/a003e00.virtio_mmio':
    KERNELS=="a003e00.virtio_mmio"
    SUBSYSTEMS=="platform"
    DRIVERS=="virtio-mmio"
    ATTRS{driver_override}=="(null)"

  looking at parent device '/devices/platform':
    KERNELS=="platform"
    SUBSYSTEMS==""
    DRIVERS==""



Regards,
Daniel
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