Re: [Qemu-devel] [PATCH 2/3] hw/virtio-net.c: set config size using host features

[Anthony Liguori]

"Michael S. Tsirkin" <address@hidden> writes:

> On Thu, Feb 07, 2013 at 09:45:54AM -0600, Anthony Liguori wrote:
>> "Michael S. Tsirkin" <address@hidden> writes:
>> 
>> This is about bug-for-bug compatibility with older QEMU.
>
> Sorry, with which version?
>
> It looks like if I run qemu 1.3 with .status=off
> windows drivers work. If I do this on 1.4 they break.
> I don't see much value in knowingly breaking working setups
> like this.

The whole discussion is moot because there's no version of QEMU that we
support backwards compatibility for that didn't have status enabled by
default.

What we need to worry about supporting is compat machines.  Not random
combination of feature flags that no actual user uses.

As a general rule, we need to make sure that the devices we expose look
the same when doing -M.  That means the config space size needs to be
the same as it was in previous machines.  This is a pretty simple
thing.

Regards,

Anthony Liguori

>
> -- 
> MST