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Re: [libvirt] [PATCH 1/5] S390: Documentation for CCW address type



On Thu, Jan 31, 2013 at 02:46:26PM +0100, Viktor Mihajlovski wrote:
> The native bus for s390 I/O is called CCW (channel command word).
> As QEMU has added basic support for the CCW bus, i.e. the
> ability to assign CCW devnos (bus addresses) to devices.
> Domains with the new machine type s390-ccw-virtio can use the
> CCW bus. Currently QEMU will only allow to define virtio
> devices on the CCW bus.
> Here we add the new machine type and the new device address to the
> schema definition and add a new paragraph to the domain XML
> documentation.
> 
> Signed-off-by: Viktor Mihajlovski <mihajlov linux vnet ibm com>
> ---
>  docs/formatdomain.html.in     |   12 ++++++++++++
>  docs/schemas/domaincommon.rng |   21 +++++++++++++++++++++
>  2 files changed, 33 insertions(+)
> 
> diff --git a/docs/formatdomain.html.in b/docs/formatdomain.html.in
> index c01f564..1dac880 100644
> --- a/docs/formatdomain.html.in
> +++ b/docs/formatdomain.html.in
> @@ -2018,6 +2018,18 @@
>          of the starting register).  <span class="since">Since
>          0.9.9.</span>
>        </dd>
> +      <dt><code>type='ccw'</code></dt>
> +      <dd>s390 guests with a <code>machine</code> value of
> +        s390-ccw-virtio use the native CCW bus for I/O devices.
> +        A CCW bus address can be specified using the additional
> +        attribute: <code>devno</code> consisting of three dot-seperated
> +        numbers composed of 2, 1 and 4 hex digits, e.g., 'fe.0.1234'.
> +        Since the current implemention of QEMU only supports virtio
> +        devices for s390 and this class of devices is restricted to
> +        channel subsystem number 'fe' by the s390 architecture, a valid
> +        devno lies in the range from 'fe.0.0000' to 'fe.3.ffff'.
> +        <span class="since">Since 1.0.3.</span>
> +      </dd>

Can you explaiin the semantics of the different components
in this device address ? WIth PCI addresses there are 4
colon-separated numbers a:b:c:d, which we explicitly
separate in the XML

  <address type="pci" domain="a" bus="b" device="c" function="d"/>

Unless there's a compelling reason not to, I think CCW
address XML ought to be similar, and use decimal notication
for each part, rather than hex, or at least require an
explicit 0x for hex. eg

  <address type="ccw" xxxx="254" yyyy="0" zzzz="1234" />
  <address type="ccw" xxxx="0xfe" yyyy="0" zzzz="1234" />

Daniel
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