Re: [PATCH] libxl: Add suppress-vmdesc to QEMU -machine pc options

[Anthony PERARD <anthony.perard@xxxxxxxxxx>]

On Mon, Oct 19, 2020 at 04:00:50PM -0400, Jason Andryuk wrote:
> The device model state saved by QMP xen-save-devices-state doesn't
> include the vmdesc json.  When restoring an HVM, xen-load-devices-state
> always triggers "Expected vmdescription section, but got 0".  This is
> not a problem when restore comes from a file.  However, when QEMU runs
> in a linux stubdom and comes over a console, EOF is not received.  This
> causes a delay restoring - though it does restore.
> 
> Setting suppress-vmdesc skips looking for the vmdesc during restore and
> avoids the wait.
> 
> This is a libxl change for the non-xenfv case to match the xenfv change
> made in qemu
> 
> Signed-off-by: Jason Andryuk <jandryuk@xxxxxxxxx>
> ---
> 
> Should this also add suppress-vmdesc to xenfv for backwards
> compatibility?  In that case, the change in QEMU is redundent.  Since
> this only really matters for the stubdom case, it could be conditioned
> on that.

QEMU doesn't complain about having suppress-vmdesc set on the command
line and as a default for the xenfv machine, so I don't mind adding it
to the xenfv machine in libxl, while keeping the change in QEMU.

The change is already applied to QEMU, so unless there's an issue, I
don't want to revert it. It might be useful for tool stacks that don't
use libxl.

Also, the change matters as well for non-stubdom cases as it removed a
cryptic error message from qemu-dm's logs :-).

Thanks,

-- 
Anthony PERARD