[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

Re: [libvirt] [PATCH] qemu: Restored original console alias



On Fri, Jun 28, 2013 at 01:11:40PM +0200, Michal Privoznik wrote:
> Because of some crazy backward compatibility, console device is in
> some cases just an alias to a serial device. This means, in the process
> of generating XML description of a domain, all the interesting info is
> taken from corresponding serial device, if that's the case. Including
> the device alias. That means, we produce:
>     <console type='pty' tty='/dev/pts/20'>
>       ...
>       <alias name='serial0'/>
>     </console>
> 
> (notice the assigned alias)
> 
> Maybe this is okay, maybe its wrong either. Anyway, later, when libvirtd
> restarts, and we parse the state XML file, we read the wrong alias back.
> Hence, the internal representation is different to the state it was in
> prior the libvirtd restart.
> ---
>  src/qemu/qemu_domain.c | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
> 
> diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c
> index 8d79066..96d88ec 100644
> --- a/src/qemu/qemu_domain.c
> +++ b/src/qemu/qemu_domain.c
> @@ -804,6 +804,34 @@ qemuDomainDeviceDefPostParse(virDomainDeviceDefPtr dev,
>          dev->data.chr->source.data.nix.listen = true;
>      }
>  
> +    /* For some really crazy back compat in virDomainDefFormatInternal we must
> +     * restore the original console alias. For hvm domains, we are formatting
> +     * a dummy console device (based on a serial device which it refers to)
> +     * instead of the original one.  That means the device aliases in memory
> +     * and in the formatted XML are not in sync. While in memory we still have
> +     * 'consoleN', in the formatted XML we have 'serialN'. */
> +    if (dev->type == VIR_DOMAIN_DEVICE_CHR &&
> +        dev->data.chr->deviceType == VIR_DOMAIN_CHR_DEVICE_TYPE_CONSOLE &&
> +        dev->data.chr->targetType == VIR_DOMAIN_CHR_CONSOLE_TARGET_TYPE_SERIAL &&
> +        STREQ(def->os.type, "hvm")) {
> +        int id;
> +        char *alias = dev->data.chr->info.alias;
> +        const char *serial_alias = "serial";
> +
> +        if (alias && STRPREFIX(alias, serial_alias)) {
> +            alias += strlen(serial_alias);
> +
> +            if (virStrToLong_i(alias, NULL, 10, &id) < 0)
> +                goto cleanup;
> +
> +            VIR_FREE(dev->data.chr->info.alias);
> +            if (virAsprintf(&dev->data.chr->info.alias, "console%d", id) < 0) {
> +                virReportOOMError();
> +                goto cleanup;
> +            }
> +        }
> +    }
> +
>      ret = 0;
>  
>  cleanup:

Ok, the situation we have is

  - The VM is configured with a <serial> port

  - The <serial> port config is copied to <console> for purposes of
    back compatibility

  - After starting the guest

      QEMU has a device with id==serial0

    while virDomainDefPtr has

      def->seriales[0]->info == "serial0"
      def->consoles[0]->info == "console0"

    and the XML shown to the user, and saved to the state XML is

      <serial type='pty'>
        <source path='/dev/pts/7'/>
        <target port='0'/>
        <alias name='serial0'/>
      </serial>
      <console type='pty' tty='/dev/pts/7'>
        <source path='/dev/pts/7'/>
        <target type='serial' port='0'/>
        <alias name='serial0'/>
      </console>


    This inconsistency/inaccuracy in the virDomainDefPtr is bad

  - After re-starting libvirtd, while the guest is runing

      def->seriales[0]->info == "serial0"
      def->consoles[0]->info == "serial0"

    because it got this data from the state XML file and
    the XML shown to the user remains:

      <serial type='pty'>
        <source path='/dev/pts/7'/>
        <target port='0'/>
        <alias name='serial0'/>
      </serial>
      <console type='pty' tty='/dev/pts/7'>
        <source path='/dev/pts/7'/>
        <target type='serial' port='0'/>
        <alias name='serial0'/>
      </console>

    So the inconsistency has been fixed at this point



IIUC, this patch is intended to change things so that after libvirtd is
restarted, we get:

      def->seriales[0]->info == "serial0"
      def->consoles[0]->info == "console0"

but this is fixing the wrong thing. There is only one physical device
emulated in the guest, which is a serial port with id==serial0, and
this is reflected correctly in the XML we generate. Only the internal
struct is different.

So what needs fixing is the code which populated def->consoles[0]->info
with "console0" instead of the correct "serial0" string at VM startup.

Regards,
Daniel
-- 
|: http://berrange.com      -o-    http://www.flickr.com/photos/dberrange/ :|
|: http://libvirt.org              -o-             http://virt-manager.org :|
|: http://autobuild.org       -o-         http://search.cpan.org/~danberr/ :|
|: http://entangle-photo.org       -o-       http://live.gnome.org/gtk-vnc :|


[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]