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Re: [Xen-devel] [PATCH 2/8] x86/setup: Fix badpage= handling for memory above HYPERVISOR_VIRT_END

Hi David,

On 01/02/2020 00:32, David Woodhouse wrote:
   * Hand the specified arbitrary page range to the specified heap zone
   * checking the node_id of the previous page.  If they differ and the
@@ -1799,18 +1811,23 @@ static void init_heap_pages(
          unsigned int nid = phys_to_nid(page_to_maddr(pg+i));
+ /* If the (first) page is already marked broken, don't add it. */
+        if ( pg[i].count_info & PGC_broken )
+            continue;
          if ( unlikely(!avail[nid]) )
+            unsigned long contig_nr_pages = contig_avail_pages(pg + i, 

I spent the evening chasing a bug due to this change. Xen may give to init_heap_pages() a range that crosses NUMA node.

contig_avail_pages will go through the range [pg + 1, pg + i + nr_pages). As nr_pages corresponds to the number of pages in the original range, we may overrun the frametable and crash.

So I think you want to use contig_avail_pages(pg + i, nr_pages - i).


Julien Grall

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