xen/balloon: before adding hotplugged memory, set frames to invalid

Commit 25b884a83d487fd62c3de7ac1ab5549979188482 ("x86/xen: set
regions above the end of RAM as 1:1") introduced a regression.

To be able to add memory pages which were added via memory hotplug to
a pv domain, the pages must be "invalid" instead of "identity" in the
p2m list before they can be added.

Suggested-by: David Vrabel <david.vrabel@citrix.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Cc: <stable@vger.kernel.org> # 3.16+
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 0b52d92..fd93369 100644 (file)
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -229,6 +229,29 @@ static enum bp_state reserve_additional_memory(long credit)
        balloon_hotplug = round_up(balloon_hotplug, PAGES_PER_SECTION);
        nid = memory_add_physaddr_to_nid(hotplug_start_paddr);
 
+#ifdef CONFIG_XEN_HAVE_PVMMU
+        /*
+         * add_memory() will build page tables for the new memory so
+         * the p2m must contain invalid entries so the correct
+         * non-present PTEs will be written.
+         *
+         * If a failure occurs, the original (identity) p2m entries
+         * are not restored since this region is now known not to
+         * conflict with any devices.
+         */ 
+       if (!xen_feature(XENFEAT_auto_translated_physmap)) {
+               unsigned long pfn, i;
+
+               pfn = PFN_DOWN(hotplug_start_paddr);
+               for (i = 0; i < balloon_hotplug; i++) {
+                       if (!set_phys_to_machine(pfn + i, INVALID_P2M_ENTRY)) {
+                               pr_warn("set_phys_to_machine() failed, no memory added\n");
+                               return BP_ECANCELED;
+                       }
+                }
+       }
+#endif
+
        rc = add_memory(nid, hotplug_start_paddr, balloon_hotplug << PAGE_SHIFT);
 
        if (rc) {