xen/balloon: set a mapping for ballooned out pages
Currently ballooned out pages are mapped to 0 and have INVALID_P2M_ENTRY
in the p2m. These ballooned out pages are used to map foreign grants
by gntdev and blkback (see alloc_xenballooned_pages).
Allocate a page per cpu and map all the ballooned out pages to the
corresponding mfn. Set the p2m accordingly. This way reading from a
ballooned out page won't cause a kernel crash (see
http://lists.xen.org/archives/html/xen-devel/2012-12/msg01154.html).
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
CC: alex@alex.org.uk
CC: dcrisan@flexiant.com
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
diff --git a/include/xen/balloon.h b/include/xen/balloon.h
index cc2e1a7..a4c1c6a 100644
--- a/include/xen/balloon.h
+++ b/include/xen/balloon.h
@@ -29,6 +29,9 @@
bool highmem);
void free_xenballooned_pages(int nr_pages, struct page **pages);
+struct page *get_balloon_scratch_page(void);
+void put_balloon_scratch_page(void);
+
struct device;
#ifdef CONFIG_XEN_SELFBALLOONING
extern int register_xen_selfballooning(struct device *dev);