Re: fix for "xen: use maximum reservation to limit amount of usable RAM" - patch titled: "xen/e820: if there is not dom0_mem, don't tweak extra_pages."

[David Vrabel <david.vrabel@citrix.com>]

On 12/09/11 21:13, Konrad Rzeszutek Wilk wrote:
> .breaks one of my boxes (Core i3-2100), with Xen 4.1.1 (with and w/out the
> 23790 changset in it).
> 
> I've traced it down to the fact that I booted my dom0 without
> dom0_mem=X flag with a machine that has more than 8GB. Weirdly enough
> I can only reproduce this under Intel boxes.
> 
> Anyhow this patch fixes it for me.

I think this patch is simpler.  Does it fix the issue?

diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index c3b8d44..46d6d21 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -306,10 +306,12 @@ char * __init xen_memory_setup(void)
 	sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);
 
 	extra_limit = xen_get_max_pages();
-	if (extra_limit >= max_pfn)
-		extra_pages = extra_limit - max_pfn;
-	else
-		extra_pages = 0;
+	if (max_pfn + extra_pages > extra_limit) {
+		if (extra_limit > max_pfn)
+			extra_pages = extra_limit - max_pfn;
+		else
+			extra_pages = 0;
+	}
 
 	extra_pages += xen_return_unused_memory(xen_start_info->nr_pages, &e820);
 
David