Win2003 got blue Screen when ballooning with serial out put: "Iomem mapping not permitted"

[tinnycloud <tinnycloud@hotmail.com>]

Hi Steven:

	I was trying to make use of balloon driver on my win2003 HVM Guests,
but confront a Guest crash problem with blue screen.
	The serial output is much like 
	(XEN)grant_table.c:555:d0 Iomem mapping not permitted
ffffffffffffffff

	My pvdriver changeset is 823. From
http://xenbits.xensource.com/ext/win-pvdrivers.hg
	Xen is 4.0.0

	I've done quite a lot experiments to locate the crash, and finally
make it easy to reproduce.
	Here is the situation:

	1) Start several Win2003 Guest with 2G memory to occupy host memory
till from xm info | grep free to see xen has only almost 3G memory
	2) Start another Guest with 2G memory, say domain X, and set its
target to be 512M, after balloon, dom X will has only 512M, and xen has 2.5G
memory
	3) Start another Guest with 2G memory, then xen will have only 0.5G
memory left
	4) At this time, I set the domain X target to 2G (use xenstore-write
/local/domain/x/memory/target 2097152)
    5) domain X got blue screen at once. With code says 0x0000007f
(0x0000000d, 0x00000000, 0x00000000, 0x00000000)"

	So, in short, when a domain wants more memory, it deflates its
balloon, but if Xen doesn't enough memory, the domain will crash.

	I've go through
http://lists.xensource.com/archives/html/xen-devel/2010-01/msg01230.html
	
http://lists.xensource.com/archives/html/xen-devel/2010-02/msg00074.html

	it looks like the crash is because windows crash dumper go through
those balloon out pages
	and from the discuss it would be harmless, but why I got this crash?
	
	Could you kindly offer me some help, thanks.