[BUG] mm locking order violation when HVM guest changes graphics mode on virtual graphics adapter.

[Austin S Hemmelgarn <ahferroin7@gmail.com>]

Reliably reproducible, occurs when HVM guest changes graphics mode
virtual graphics adapter on Xen 4.3.0 from Gentoo.

To reproduce: Using Xen 4.3.0 from Gentoo Portage Tree, and the
corresponding version of Xl, both built with GCC 4.7.3 with HVM and
qemu-dm support built in:
1. Boot using a Gentoo Linux Dom0 with kernel version 3.10.7-r1 built
with the kernel config found at http://pastebin.com/GxDpPsk3.
2. Get a copy of the fedora i686 network install CD.
2. Start a HVM domain with a configuration like the one found at
http://pastebin.com/p0wxnaTg.
3. After connecting to the VNC console, start the install process.
4. When Anaconda tries to start the graphical environment, causing the
kernel to change the graphics mode from the current setting, xen will
crash with a call to BUG() in mm.h at line 118.

Xen log can be found at http://pastebin.com/zKCJsp21.
xl info output can be found at http://pastebin.com/NqtksS18.
lspci -vvv output can be found at http://pastebin.com/Ja97Cx42.
xenstore contents can be found at http://pastebin.com/aL9vpxwu.

I'll be happy to provide any other information you may need upon request.