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

3 files changed, 49 insertions, 1 deletions

diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 9f93af56a5fc..b47124d4cd67 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -91,6 +91,12 @@ EXPORT_SYMBOL_GPL(xen_p2m_size);
 unsigned long xen_max_p2m_pfn __read_mostly;
 EXPORT_SYMBOL_GPL(xen_max_p2m_pfn);
 
+#ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG_LIMIT
+#define P2M_LIMIT CONFIG_XEN_BALLOON_MEMORY_HOTPLUG_LIMIT
+#else
+#define P2M_LIMIT 0
+#endif
+
 static DEFINE_SPINLOCK(p2m_update_lock);
 
 static unsigned long *p2m_mid_missing_mfn;
@@ -385,9 +391,11 @@ static void __init xen_rebuild_p2m_list(unsigned long *p2m)
 void __init xen_vmalloc_p2m_tree(void)
 {
         static struct vm_struct vm;
+        unsigned long p2m_limit;
 
+        p2m_limit = (phys_addr_t)P2M_LIMIT * 1024 * 1024 * 1024 / PAGE_SIZE;
         vm.flags = VM_ALLOC;
-        vm.size = ALIGN(sizeof(unsigned long) * xen_max_p2m_pfn,
+        vm.size = ALIGN(sizeof(unsigned long) * max(xen_max_p2m_pfn, p2m_limit),
                         PMD_SIZE * PMDS_PER_MID_PAGE);
         vm_area_register_early(&vm, PMD_SIZE * PMDS_PER_MID_PAGE);
         pr_notice("p2m virtual area at %p, size is %lx\n", vm.addr, vm.size);
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) {