Eric W. Biederman wrote:

....
+Field name:	hardware_subarch
+Type:		write
+Offset/size:	0x23c/4
+Protocol:	2.07+
+
+  In a paravirtualized environment the hardware low level architectural 
+  pieces such as interrupt handling, page table handling, and
+  accessing process control registers needs to be done differently.
+
+  This field allows the bootloader to inform the kernel we are in one
+  one of those environments.
+
+  0x00000000	The default x86/PC environment
+  0x00000001	lguest
+  0x00000002	Xen
+
+Field name:	hardware_subarch_data
+Type:		write
+Offset/size:	0x23c/8
  

offset = 240

+Protocol:	2.07+
+
+  A pointer to data that is specific to hardware subarch
  

Do we care particularly? If 8 bytes is enough for the subarch, do we
care whether its a pointer or literal? After all, this is just a private
channel between the bootloader and some subarch-specific piece of code
in the kernel.

J