xen: branch for v6.15-rc2

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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

arch/x86/xen/enlighten.c

@@ -70,6 +70,9 @@ EXPORT_SYMBOL(xen_start_flags);
  */
 struct shared_info *HYPERVISOR_shared_info = &xen_dummy_shared_info;
 
+/* Number of pages released from the initial allocation. */
+unsigned long xen_released_pages;
+
 static __ref void xen_get_vendor(void)
 {
 	init_cpu_devs();
@@ -466,6 +469,13 @@ int __init arch_xen_unpopulated_init(struct resource **res)
 			xen_free_unpopulated_pages(1, &pg);
 		}
 
+		/*
+		 * Account for the region being in the physmap but unpopulated.
+		 * The value in xen_released_pages is used by the balloon
+		 * driver to know how much of the physmap is unpopulated and
+		 * set an accurate initial memory target.
+		 */
+		xen_released_pages += xen_extra_mem[i].n_pfns;
 		/* Zero so region is not also added to the balloon driver. */
 		xen_extra_mem[i].n_pfns = 0;
 	}

arch/x86/xen/enlighten_pvh.c

@@ -1,5 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <linux/acpi.h>
+#include <linux/cpufreq.h>
+#include <linux/cpuidle.h>
 #include <linux/export.h>
 #include <linux/mm.h>
 
@@ -123,8 +125,23 @@ static void __init pvh_arch_setup(void)
 {
 	pvh_reserve_extra_memory();
 
-	if (xen_initial_domain())
+	if (xen_initial_domain()) {
 		xen_add_preferred_consoles();
+
+		/*
+		 * Disable usage of CPU idle and frequency drivers: when
+		 * running as hardware domain the exposed native ACPI tables
+		 * causes idle and/or frequency drivers to attach and
+		 * malfunction.  It's Xen the entity that controls the idle and
+		 * frequency states.
+		 *
+		 * For unprivileged domains the exposed ACPI tables are
+		 * fabricated and don't contain such data.
+		 */
+		disable_cpuidle();
+		disable_cpufreq();
+		WARN_ON(xen_set_default_idle());
+	}
 }
 
 void __init xen_pvh_init(struct boot_params *boot_params)

arch/x86/xen/setup.c

@@ -37,9 +37,6 @@
 
 #define GB(x) ((uint64_t)(x) * 1024 * 1024 * 1024)
 
-/* Number of pages released from the initial allocation. */
-unsigned long xen_released_pages;
-
 /* Memory map would allow PCI passthrough. */
 bool xen_pv_pci_possible;
 

drivers/xen/Kconfig

@@ -278,7 +278,7 @@ config XEN_PRIVCMD_EVENTFD
 
 config XEN_ACPI_PROCESSOR
 	tristate "Xen ACPI processor"
-	depends on XEN && XEN_PV_DOM0 && X86 && ACPI_PROCESSOR && CPU_FREQ
+	depends on XEN && XEN_DOM0 && X86 && ACPI_PROCESSOR && CPU_FREQ
 	default m
 	help
 	  This ACPI processor uploads Power Management information to the Xen

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)) {

drivers/xen/xenbus/xenbus_probe_frontend.c

@@ -513,4 +513,5 @@ static int __init boot_wait_for_devices(void)
 late_initcall(boot_wait_for_devices);
 #endif
 
+MODULE_DESCRIPTION("Xen PV-device frontend support");
 MODULE_LICENSE("GPL");