Re: [Qemu-devel] [PATCH 6/6] migration: catch unknown flags in ram_load

[Eric Blake <eblake@redhat.com>]

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On 06/15/2014 09:15 PM, Juan Quintela wrote:
> From: Peter Lieven <pl@kamp.de>
> 
> if a saved vm has unknown flags in the memory data qemu
> currently simply ignores this flag and continues which
> yields in an unpredictable result.
> 
> This patch catches all unknown flags and aborts the
> loading of the vm. Additionally error reports are thrown
> if the migration aborts abnormally.

This patch is a strict improvement, so I'm glad it went in.  However, I
still feel that we aren't doing a good job of silently ignoring
unexpected combinations of flag bits, and had suggestions in the
original thread on further followups that are worth having before the
2.1 release.

> -
> -        if (flags & RAM_SAVE_FLAG_COMPRESS) {
> +        } else if (flags & RAM_SAVE_FLAG_COMPRESS) {
>              void *host;

Among other things, switching from a chain of if-else to a switch might
make it easier to document explicit supported combinations of flags and
reject other values from an invalid stream.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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