Re: [Xen-devel] [PATCH V2] libxl: Set path to console on domain startup.

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2014-12-09 at 15:39 +0000, Anthony PERARD wrote:
> The path to the pty of a Xen PV console is set only in
> virDomainOpenConsole. But this is done too late. A call to
> virDomainGetXMLDesc done before OpenConsole will not have the path to
> the pty, but a call after OpenConsole will.
> 
> e.g. of the current issue.
> Starting a domain with '<console type="pty"/>'
> Then:
> virDomainGetXMLDesc():
>   <devices>
>     <console type='pty'>
>       <target type='xen' port='0'/>
>     </console>
>   </devices>
> virDomainOpenConsole()
> virDomainGetXMLDesc():
>   <devices>
>     <console type='pty' tty='/dev/pts/30'>
>       <source path='/dev/pts/30'/>
>       <target type='xen' port='0'/>
>     </console>
>   </devices>
> 
> The patch intend to have the TTY path on the first call of GetXMLDesc.
> This is done by setting up the path at domain start up instead of in
> OpenConsole.
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=1170743
> 
> Signed-off-by: Anthony PERARD <anthony.perard@xxxxxxxxxx>
> 
> ---
> Change in V2:
>   Adding bug report link.
>   Reword the last part of the patch description.
>   Cleanup the code.
>   Use VIR_FREE before VIR_STRDUP.
>   Remove the code from OpenConsole as it is now a duplicate.
> ---
>  src/libxl/libxl_domain.c | 20 ++++++++++++++++++++
>  src/libxl/libxl_driver.c | 15 ---------------
>  2 files changed, 20 insertions(+), 15 deletions(-)
> 
> diff --git a/src/libxl/libxl_domain.c b/src/libxl/libxl_domain.c
> index 9c62291..325de79 100644
> --- a/src/libxl/libxl_domain.c
> +++ b/src/libxl/libxl_domain.c
> @@ -1290,6 +1290,26 @@ libxlDomainStart(libxlDriverPrivatePtr driver, 
> virDomainObjPtr vm,
>      if (libxlDomainSetVcpuAffinities(driver, vm) < 0)
>          goto cleanup_dom;
>  
> +    if (vm->def->nconsoles) {
> +        virDomainChrDefPtr chr = vm->def->consoles[0];

Given vm->def->nconsoles should we loop and do them all?

Also, and I really should know the answer to this (and sorry for not
thinking of it earlier), but:

> +            ret = libxl_console_get_tty(priv->ctx, vm->def->id,
> +                                        chr->target.port, console_type,
> +                                        &console);

Might this race against xenconsoled writing the node to xenstore and
therefore be prone to failing when starting multiple guests all at once?

Is there a hook which is called on virsh dumpxml which could update
things on the fly (i.e. lookup the console iff it isn't already set)?

Ian.


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