[Qemu-devel] which machinetypes have an integrated/implied IDE controller?

[Qemu-devel] which machinetypes have an integrated/implied IDE controller?

[Laine Stump]

For a long time, libvirt assumed by default that all types of virtual 
machines had an integrated IDE controller named "ide" that wasn't 
specified on the qemu commandline. Since that caused problems 
specifically for the Q35 machine type (which has an *ahci* controller 
that it perplexingly calls "ide"), I added code to libvirt to only make 
that assumption for i440fx-based machinetypes, and to log an error and 
fail in all other cases where someone tried to create a disk attached to 
an IDE controller:

  http://libvirt.org/git/?p=libvirt.git;a=commitdiff;h=eadd757

(libvirt doesn't support explicitly adding IDE controllers on the qemu 
commandline, under the assumption that 1) there are lots of better ways 
to attach a disk and 2) nobody has asked for it up to now, and we don't 
want to encourage them to start using something that is slow and 
unnecessary).

But I just received an email from someone who informed me that the 
"ppc-beigeg3" machine type also has an IDE controller, and that 
additionally this is the *only* method of connecting a disk on this 
particular machine. So now I'm wondering how I can determine what other 
machinetypes have an integrated IDE controller, so that I can add them 
to this check. (I would also like to find out which qemu binary supports 
the "ppc-beigeg3" machinetype - I tried running "qemu-blah -M ?" for 
every qemu binary on my Fedora 22 system, and didn't see anything like 
that).

Re: [Qemu-devel] which machinetypes have an integrated/implied IDE controller?

[Paolo Bonzini]

A quick "git grep -l ahci" says that in addition to q35, three ARM
boards have an AHCI controller: highbank, cubieboard (also known as
allwinner-a10) and xilinx-zynq-a9 (also known as xlnx-zynqmp).
Everything else that has IDE really means parallel ATA.

In practice the only difference between the two is that parallel ATA
distinguishes master/slave, while serial ATA has only one unit per bus
(in addition, PATA has two buses while SATA/AHCI has six).

On 12/11/2015 21:01, Laine Stump wrote:
> But I just received an email from someone who informed me that the
> "ppc-beigeg3" machine type also has an IDE controller, and that
> additionally this is the *only* method of connecting a disk on this
> particular machine.

That's not exactly true since g3beige has a PCI controller.  It may well
be that IDE is the only one supported by the firmware.

> So now I'm wondering how I can determine what other
> machinetypes have an integrated IDE controller, so that I can add them
> to this check. (I would also like to find out which qemu binary supports
> the "ppc-beigeg3" machinetype - I tried running "qemu-blah -M ?" for
> every qemu binary on my Fedora 22 system, and didn't see anything like
> that).

It's actually called g3beige. :)

Paolo

Re: [Qemu-devel] which machinetypes have an integrated/implied IDE controller?

[Markus Armbruster]

Laine Stump <laine@redhat.com> writes:

> For a long time, libvirt assumed by default that all types of virtual
> machines had an integrated IDE controller named "ide" that wasn't
> specified on the qemu commandline. Since that caused problems
> specifically for the Q35 machine type (which has an *ahci* controller
> that it perplexingly calls "ide"), I added code to libvirt to only
> make that assumption for i440fx-based machinetypes, and to log an
> error and fail in all other cases where someone tried to create a disk
> attached to an IDE controller:
>
>  http://libvirt.org/git/?p=libvirt.git;a=commitdiff;h=eadd757
>
> (libvirt doesn't support explicitly adding IDE controllers on the qemu
> commandline, under the assumption that 1) there are lots of better
> ways to attach a disk and 2) nobody has asked for it up to now, and we
> don't want to encourage them to start using something that is slow and
> unnecessary).
>
> But I just received an email from someone who informed me that the
> "ppc-beigeg3" machine type also has an IDE controller, and that
> additionally this is the *only* method of connecting a disk on this
> particular machine. So now I'm wondering how I can determine what
> other machinetypes have an integrated IDE controller, so that I can
> add them to this check. (I would also like to find out which qemu
> binary supports the "ppc-beigeg3" machinetype - I tried running
> "qemu-blah -M ?" for every qemu binary on my Fedora 22 system, and
> didn't see anything like that).

Basically, your problem is to find the plugs provided by the board, for
each machine type.

I figure the sane way to find them is QOM introspection: walk the QOM
tree and collect the plugs.

Beware, I'm only superficially familiar with QOM, so my explanations may
be off.  Cc'ing Andreas, who can hopefully correct my mistakes.

The relevant QMP commands are qom-list and qom-get.  But to explore the
QOM tree, I rather like "info qom-tree" (sadly, still HMP only) and
scripts/qmp/qom-fuse (which uses qom-list and qom-get under the hood).

Start QEMU with an HMP monitor on stdio and a QMP monitor on
/wherever/qmp-socket, and run "info qom-tree":

    $ qemu-system-x86_64 -nodefaults -S -display none -monitor stdio -chardev id=chr-qmp,backend=socket,path=test-qmp,server,nowait -mon mode=control,id=mon-qmp,chardev=chr-qmp
    QEMU 2.4.50 monitor - type 'help' for more information
    (qemu) info qom-tree
    /machine (pc-i440fx-2.5-machine)
      /unattached (container)
      [...]
        /device[16] (piix3-ide)
          /bus master[0] (qemu:memory-region)
          /piix-bmdma-container[0] (qemu:memory-region)
          /piix-bmdma[0] (qemu:memory-region)
          /bmdma[0] (qemu:memory-region)
          /piix-bmdma[1] (qemu:memory-region)
          /bmdma[1] (qemu:memory-region)
          /ide.0 (IDE)
          /ide.1 (IDE)
      [...]

In another terminal, run

    $ QMP_SOCKET=/wherever/qmp-socket scripts/qmp/qom-fuse /mount/point
    $ cd /mount/point

Now let's explore a bit.

    $ cd machine/unattached/device\[16\]
    $ ls -F
    addr                 hotpluggable  multifunction             realized
    bmdma[0]/            hotplugged    parent_bus@               rombar
    bmdma[1]/            ide.0/        piix-bmdma-container[0]/  romfile
    bus master[0]/       ide.1/        piix-bmdma[0]/            type
    command_serr_enable  legacy-addr   piix-bmdma[1]/
    $ cat type 
    piix3-ide

This is the device model.

    $ ls -l parent_bus
    lrwxr-xr-x. 2 armbru armbru 4096 Jan  1  1970 parent_bus -> ../../../machine/i440fx/pci.0

This is the bus it's plugged in, and its name is "pci.0".

    $ cat parent_bus/type 
    PCI

It's a PCI bus (surprise, surprise).

    $ cat addr 
    9

Our piix3-ide's PCI address 01.1 (encoded as decimal integer).

    $ ls -F ide.0
    hotplug-handler@  realized  type
    $ cat ide.0/type 
    IDE

Aha, this is a bus, the bus type is IDE, and its name is "ide.0".

When you're done, don't forget to kill qom-fuse.

Hope this helps!