Page scrubbing

Hi!

Make scrub_heap_pages() print from where to where
it scrubs pages.

This patch uncovers a strange behaviour on 32bit.
On 64bit I get this:

(XEN) Scrubbing Free RAM 0xffff830000100000 -> 0xffff83003fff0000: ....done.

On 32bit I get this:

(XEN) Scrubbing Free RAM 0xffc00000 ->
0xdefb0000: .............................done.

On 64bit the scrubber goes up, but on 32bit it goes down. Is this behaviour expected?

AMD Saxony, Dresden, Germany
Operating System Research Center

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   Dr. Hans-R. Deppe, Thomas McCoy

diff -r 9071521d4864 xen/common/page_alloc.c
@@ -596,7 +596,9 @@ void __init scrub_heap_pages(void)
     if ( !opt_bootscrub )
         return;
 
-    printk("Scrubbing Free RAM: ");
+    printk("Scrubbing Free RAM 0x%p -> 0x%p: ",
+        page_to_virt(mfn_to_page(first_valid_mfn)),
+        page_to_virt(mfn_to_page(max_page)));
 
     for ( mfn = first_valid_mfn; mfn < max_page; mfn++ )
     {

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The printk() is printing nonsense for x86/32, as most pages do not have a permanent mapping in Xen, and hence no valid virtual address. Page_to_virt() on such pages is not allowed.

-- Keir