xen/balloon: simplify test for the end of usable RAM

When initializing the balloon only max_pfn needs to be checked
(max_pfn will always be <= e820_end_of_ram_pfn()) and improve the
confusing comment.

Signed-off-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
This commit is contained in:
David Vrabel 2011-09-28 17:46:33 +01:00 committed by Konrad Rzeszutek Wilk
parent aa24411b67
commit b1cbf9b1d6

View File

@ -586,16 +586,16 @@ static int __init balloon_init(void)
#endif
/*
* Initialise the balloon with excess memory space. We need
* to make sure we don't add memory which doesn't exist or
* logically exist. The E820 map can be trimmed to be smaller
* than the amount of physical memory due to the mem= command
* line parameter. And if this is a 32-bit non-HIGHMEM kernel
* on a system with memory which requires highmem to access,
* don't try to use it.
* Initialize the balloon with pages from the extra memory
* region (see arch/x86/xen/setup.c).
*
* If the amount of usable memory has been limited (e.g., with
* the 'mem' command line parameter), don't add pages beyond
* this limit.
*/
extra_pfn_end = min(min(max_pfn, e820_end_of_ram_pfn()),
(unsigned long)PFN_DOWN(xen_extra_mem_start + xen_extra_mem_size));
extra_pfn_end = min(max_pfn,
(unsigned long)PFN_DOWN(xen_extra_mem_start
+ xen_extra_mem_size));
for (pfn = PFN_UP(xen_extra_mem_start);
pfn < extra_pfn_end;
pfn++) {