Merge tag 'for-linus-6.15a-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen fixes from Juergen Gross:

 - A simple fix adding the module description of the Xenbus frontend
   module

 - A fix correcting the xen-acpi-processor Kconfig dependency for PVH
   Dom0 support

 - A fix for the Xen balloon driver when running as Xen Dom0 in PVH mode

 - A fix for PVH Dom0 in order to avoid problems with CPU idle and
   frequency drivers conflicting with Xen

* tag 'for-linus-6.15a-rc2-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  x86/xen: disable CPU idle and frequency drivers for PVH dom0
  x86/xen: fix balloon target initialization for PVH dom0
  xen: Change xen-acpi-processor dom0 dependency
  xenbus: add module description

1 files changed, 24 insertions, 10 deletions

diff --git a/drivers/xen/balloon.c b/drivers/xen/balloon.c
index 65d4e7fa1eb8..8c852807ba1c 100644
--- a/drivers/xen/balloon.c
+++ b/drivers/xen/balloon.c
@@ -679,7 +679,7 @@ void xen_free_ballooned_pages(unsigned int nr_pages, struct page **pages)
 }
 EXPORT_SYMBOL(xen_free_ballooned_pages);
 
-static void __init balloon_add_regions(void)
+static int __init balloon_add_regions(void)
 {
 	unsigned long start_pfn, pages;
 	unsigned long pfn, extra_pfn_end;
@@ -702,26 +702,38 @@ static void __init balloon_add_regions(void)
 		for (pfn = start_pfn; pfn < extra_pfn_end; pfn++)
 			balloon_append(pfn_to_page(pfn));
 
-		balloon_stats.total_pages += extra_pfn_end - start_pfn;
+		/*
+		 * Extra regions are accounted for in the physmap, but need
+		 * decreasing from current_pages to balloon down the initial
+		 * allocation, because they are already accounted for in
+		 * total_pages.
+		 */
+		if (extra_pfn_end - start_pfn >= balloon_stats.current_pages) {
+			WARN(1, "Extra pages underflow current target");
+			return -ERANGE;
+		}
+		balloon_stats.current_pages -= extra_pfn_end - start_pfn;
 	}
+
+	return 0;
 }
 
 static int __init balloon_init(void)
 {
 	struct task_struct *task;
+	int rc;
 
 	if (!xen_domain())
 		return -ENODEV;
 
 	pr_info("Initialising balloon driver\n");
 
-#ifdef CONFIG_XEN_PV
-	balloon_stats.current_pages = xen_pv_domain()
-		? min(xen_start_info->nr_pages - xen_released_pages, max_pfn)
-		: get_num_physpages();
-#else
-	balloon_stats.current_pages = get_num_physpages();
-#endif
+	if (xen_released_pages >= get_num_physpages()) {
+		WARN(1, "Released pages underflow current target");
+		return -ERANGE;
+	}
+
+	balloon_stats.current_pages = get_num_physpages() - xen_released_pages;
 	balloon_stats.target_pages  = balloon_stats.current_pages;
 	balloon_stats.balloon_low   = 0;
 	balloon_stats.balloon_high  = 0;
@@ -738,7 +750,9 @@ static int __init balloon_init(void)
 	register_sysctl_init("xen/balloon", balloon_table);
 #endif
 
-	balloon_add_regions();
+	rc = balloon_add_regions();
+	if (rc)
+		return rc;
 
 	task = kthread_run(balloon_thread, NULL, "xen-balloon");
 	if (IS_ERR(task)) {