Re: [Xen-devel] [PATCH] libxl: set channel devid when not provided by application

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Wed, Feb 07, 2018 at 08:04:10PM -0700, Jim Fehlig wrote:
> Applications like libvirt may not populate a device devid field,
> delegating that to libxl. If needed, the application can later
> retrieve the libxl-produced devid. Indeed most devices are handled
> this way in libvirt, channel devices included.
> 
> This works well when only one channel device is defined, but more
> than one results in
> 
> qemu-system-i386: -chardev socket,id=libxl-channel-1,\
> path=/tmp/test-org.qemu.guest_agent.00,server,nowait:
> Duplicate ID 'libxl-channel-1' for chardev
> 
> Besides the odd '-1' value in the id, multiple channels have the same
> id, causing qemu to fail. A simple fix is to set an uninitialized
> devid (-1) to the dev_num passed to libxl__init_console_from_channel().
> 
> Signed-off-by: Jim Fehlig <jfehlig@xxxxxxxx>
> ---
> 
> I get the feeling that if needed devid should be set earlier, but
> this seems like the most opportune spot. Suggestions for improvements
> welcome.
> 
>  tools/libxl/libxl_console.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/tools/libxl/libxl_console.c b/tools/libxl/libxl_console.c
> index 39d8430df8..8faf3a24f3 100644
> --- a/tools/libxl/libxl_console.c
> +++ b/tools/libxl/libxl_console.c
> @@ -401,6 +401,9 @@ int libxl__init_console_from_channel(libxl__gc *gc,
>  
>      /* Perform validation first, allocate second. */
>  
> +    if (channel->devid == -1)
> +        channel->devid = dev_num;

This chunk looks fine, but below in this function there's a:

console->devid = dev_num;

Which needs to be replaced with:

console->devid = channel->devid;

In this same patch.

Thanks, Roger.

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