x86/pass-through: documents as security-unsupported when sharing resources

x86/pass-through: documents as security-unsupported when sharing resources

When multiple devices share resources and one of them is to be passed
through to a guest, security of the entire system and of respective
guests individually cannot really be guaranteed without knowing
internals of any of the involved guests.  Therefore such a configuration
cannot really be security-supported, yet making that explicit was so far
missing.

This is XSA-461 / CVE-2024-31146.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
master commit: 9c94eda1e3790820699a6de3f6a7c959ecf30600
master date: 2024-08-13 16:37:25 +0200