[Bug 195537] [xen] vt console somehow causes failures to boot and disk errors

[bugzilla-noreply at freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=195537

Roger Pau Monné <royger at freebsd.org> changed:

           What    |Removed                     |Added
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           Assignee|freebsd-xen at FreeBSD.org     |royger at freebsd.org

--- Comment #1 from Roger Pau Monné <royger at freebsd.org> ---
Created attachment 150078
  --> https://bugs.freebsd.org/bugzilla/attachment.cgi?id=150078&action=edit
Make vt_vga reserve the memory it uses

Yes, I'm aware of the issue. It comes from the fact that FreeBSD/Xen uses the
holes in the memory map to map the grant table, foreign memory from other
domains, &c.

The problem is that the vt_vga driver doesn't reserve the memory region it
uses, so Xen will happily use it for it's ends, this as you already realized
ends up very badly.

I'm attaching a crappy patch that solves this by making vt_vga register the
memory it uses, but the patch is incomplete:

 * It unconditionally reserves the memory, even if vt_vga is not used.
 * I've not checked if other vt_* drivers have the same issue.

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