xen: handle highmem pages correctly when shrinking a domain

Commit 1058a75f07b9bb8323fb5197be5526220f8b75cf ("xen: actually release
memory when shrinking domain") causes a crash if the page being released
is a highmem page.

If a page is highmem then there is no need to unmap it.

Signed-off-by: Ian Campbell <ian.campbell@citrix.com>
Acked-by: Jeremy Fitzhardinge <jeremy@goop.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 7 insertions, 4 deletions

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 8069d520c460..2ba8f95516a0 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -299,10 +299,13 @@ static int decrease_reservation(unsigned long nr_pages)
 
                 scrub_page(page);
 
-                ret = HYPERVISOR_update_va_mapping(
-                        (unsigned long)__va(pfn << PAGE_SHIFT),
-                        __pte_ma(0), 0);
-                BUG_ON(ret);
+                if (!PageHighMem(page)) {
+                        ret = HYPERVISOR_update_va_mapping(
+                                (unsigned long)__va(pfn << PAGE_SHIFT),
+                                __pte_ma(0), 0);
+                        BUG_ON(ret);
+                }
+
         }
 
         /* Ensure that ballooned highmem pages don't have kmaps. */