Merge tag 'stable/for-linus-4.0-rc6-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen regression fixes from David Vrabel:
 "Fix two regressions in the balloon driver's use of memory hotplug when
  used in a PV guest"

* tag 'stable/for-linus-4.0-rc6-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen/balloon: before adding hotplugged memory, set frames to invalid
  x86/xen: prepare p2m list for memory hotplug

2 files changed, 40 insertions, 0 deletions

diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
index b812462083fc..94d96809e686 100644
--- a/drivers/xen/Kconfig
+++ b/drivers/xen/Kconfig
@@ -55,6 +55,23 @@ config XEN_BALLOON_MEMORY_HOTPLUG
 
 	  In that case step 3 should be omitted.
 
+config XEN_BALLOON_MEMORY_HOTPLUG_LIMIT
+	int "Hotplugged memory limit (in GiB) for a PV guest"
+	default 512 if X86_64
+	default 4 if X86_32
+	range 0 64 if X86_32
+	depends on XEN_HAVE_PVMMU
+	depends on XEN_BALLOON_MEMORY_HOTPLUG
+	help
+	  Maxmium amount of memory (in GiB) that a PV guest can be
+	  expanded to when using memory hotplug.
+
+	  A PV guest can have more memory than this limit if is
+	  started with a larger maximum.
+
+	  This value is used to allocate enough space in internal
+	  tables needed for physical memory administration.
+
 config XEN_SCRUB_PAGES
 	bool "Scrub pages before returning them to system"
 	depends on XEN_BALLOON
diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 0b52d92cb2e5..fd933695f232 100644
--- 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) {