Re: [Qemu-devel] [PATCH] mark nic as trusted

[Anthony Liguori <anthony@codemonkey.ws>]

Jamie Lokier wrote:
> Daniel P. Berrange wrote:
>   
>> For new Fedora / RHEL yes, but a large number of people using virt are
>> doing so with old OS versions, and the chances of anyone retro-fitting
>> all old distros is near zero. You might get it done if they were back
>> porting the VirtIO NIC devices to old distros, but almost certainly not
>> for arbitrary NIC devices like rtl8139/e1000/etc because its a huge
>> QA testing headache to avoid regressions.
>>     
>
> In some circles, a major purpose of virtualisation is to run old OS
> versions, either copied from machines where the hardware is aging to
> keep a working system still working, or for compatibility testing.
>   

When dealing with older OSes, there really no limit in terms of what we 
can do.  For instance, there's no reason that the backported version of 
the virtio-net driver cannot expose a chardev interface if the distro 
doesn't have the appropriate configuration.

But we also have to think about how to support newer platforms and newer 
kernels and this will often mean that we have to make intrusive changes 
so that the integration makes everyone happy.  This does not mean that 
we cannot support older platforms though, we just have to do it a little 
differently on the older platforms.

You cannot get around having a kernel module to support something like 
vmchannel so that's always going to be a requirement.  A completely 
userspace approach ala the VMware backdoor hackery is just too hideous.

Regards,

Anthony Liguori

> Changing a working guest setup isn't cool.  Adding a small
> monitoring/reporting app (e.g. that shows the machine's load average,
> process table, network connections or whatever over a vmchannel) may
> be cool, provided it has negligable impact, even if changing its
> system configuration is not.
>
> -- Jamie
>
>
>