xen: fixes for 4.20-rc1

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Merge tag 'for-linus-4.20a-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip

Pull xen fixes from Juergen Gross:
 "Only several small fixes and cleanups this time"

* tag 'for-linus-4.20a-rc1-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip:
  xen: drop writing error messages to xenstore
  xen/pvh: don't try to unplug emulated devices
  add myself as reviewer for Xen support in Linux
  xen: remove redundant 'default n' from Kconfig
  xen/balloon: Support xend-based toolstack
  xen/pvh: increase early stack size
  xen: make xen_qlock_wait() nestable
  xen: fix race in xen_qlock_wait()
  xen/balloon: Grammar s/Is it/It is/
  xen: Make XEN_BACKEND selectable by DomU

MAINTAINERS

@@ -16317,6 +16317,7 @@ F:	arch/arm64/include/asm/xen/
 XEN HYPERVISOR INTERFACE
 M:	Boris Ostrovsky <boris.ostrovsky@oracle.com>
 M:	Juergen Gross <jgross@suse.com>
+R:	Stefano Stabellini <sstabellini@kernel.org>
 L:	xen-devel@lists.xenproject.org (moderated for non-subscribers)
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/xen/tip.git
 S:	Supported

arch/x86/xen/platform-pci-unplug.c

@@ -134,6 +134,10 @@ void xen_unplug_emulated_devices(void)
 {
 	int r;
 
+	/* PVH guests don't have emulated devices. */
+	if (xen_pvh_domain())
+		return;
+
 	/* user explicitly requested no unplug */
 	if (xen_emul_unplug & XEN_UNPLUG_NEVER)
 		return;

arch/x86/xen/spinlock.c

@@ -39,34 +39,25 @@ static void xen_qlock_kick(int cpu)
  */
 static void xen_qlock_wait(u8 *byte, u8 val)
 {
+	unsigned long flags;
 	int irq = __this_cpu_read(lock_kicker_irq);
 
 	/* If kicker interrupts not initialized yet, just spin */
-	if (irq == -1)
+	if (irq == -1 || in_nmi())
 		return;
 
-	/* clear pending */
+	/* Guard against reentry. */
-	xen_clear_irq_pending(irq);
+	local_irq_save(flags);
-	barrier();
 
-	/*
+	/* If irq pending already clear it. */
-	 * We check the byte value after clearing pending IRQ to make sure
+	if (xen_test_irq_pending(irq)) {
-	 * that we won't miss a wakeup event because of the clearing.
+		xen_clear_irq_pending(irq);
-	 *
+	} else if (READ_ONCE(*byte) == val) {
-	 * The sync_clear_bit() call in xen_clear_irq_pending() is atomic.
+		/* Block until irq becomes pending (or a spurious wakeup) */
-	 * So it is effectively a memory barrier for x86.
+		xen_poll_irq(irq);
-	 */
+	}
-	if (READ_ONCE(*byte) != val)
-		return;
 
-	/*
+	local_irq_restore(flags);
-	 * If an interrupt happens here, it will leave the wakeup irq
-	 * pending, which will cause xen_poll_irq() to return
-	 * immediately.
-	 */
-
-	/* Block until irq becomes pending (or perhaps a spurious wakeup) */
-	xen_poll_irq(irq);
 }
 
 static irqreturn_t dummy_handler(int irq, void *dev_id)

arch/x86/xen/xen-pvh.S

@@ -170,7 +170,7 @@ canary:
 	.fill 48, 1, 0
 
 early_stack:
-	.fill 256, 1, 0
+	.fill BOOT_STACK_SIZE, 1, 0
 early_stack_end:
 
 	ELFNOTE(Xen, XEN_ELFNOTE_PHYS32_ENTRY,

drivers/xen/Kconfig

@@ -12,7 +12,6 @@ config XEN_BALLOON
 config XEN_SELFBALLOONING
 	bool "Dynamically self-balloon kernel memory to target"
 	depends on XEN && XEN_BALLOON && CLEANCACHE && SWAP && XEN_TMEM
-	default n
 	help
 	  Self-ballooning dynamically balloons available kernel memory driven
 	  by the current usage of anonymous memory ("committed AS") and
@@ -27,7 +26,6 @@ config XEN_SELFBALLOONING
 
 config XEN_BALLOON_MEMORY_HOTPLUG
 	bool "Memory hotplug support for Xen balloon driver"
-	default n
 	depends on XEN_BALLOON && MEMORY_HOTPLUG
 	help
 	  Memory hotplug support for Xen balloon driver allows expanding memory
@@ -86,7 +84,7 @@ config XEN_SCRUB_PAGES_DEFAULT
 	help
 	  Scrub pages before returning them to the system for reuse by
 	  other domains.  This makes sure that any confidential data
-	  is not accidentally visible to other domains.  Is it more
+	  is not accidentally visible to other domains.  It is more
 	  secure, but slightly less efficient. This can be controlled with
 	  xen_scrub_pages=0 parameter and
 	  /sys/devices/system/xen_memory/xen_memory0/scrub_pages.
@@ -105,8 +103,7 @@ config XEN_DEV_EVTCHN
 
 config XEN_BACKEND
 	bool "Backend driver support"
-	depends on XEN_DOM0
+	default XEN_DOM0
-	default y
 	help
 	  Support for backend device drivers that provide I/O services
 	  to other virtual machines.
@@ -227,7 +224,6 @@ config XEN_PCIDEV_BACKEND
 config XEN_PVCALLS_FRONTEND
 	tristate "XEN PV Calls frontend driver"
 	depends on INET && XEN
-	default n
 	select XEN_XENBUS_FRONTEND
 	help
 	  Experimental frontend for the Xen PV Calls protocol
@@ -238,7 +234,6 @@ config XEN_PVCALLS_FRONTEND
 config XEN_PVCALLS_BACKEND
 	bool "XEN PV Calls backend driver"
 	depends on INET && XEN && XEN_BACKEND
-	default n
 	help
 	  Experimental backend for the Xen PV Calls protocol
 	  (https://xenbits.xen.org/docs/unstable/misc/pvcalls.html). It
@@ -264,7 +259,6 @@ config XEN_PRIVCMD
 config XEN_STUB
 	bool "Xen stub drivers"
 	depends on XEN && X86_64 && BROKEN
-	default n
 	help
 	  Allow kernel to install stub drivers, to reserve space for Xen drivers,
 	  i.e. memory hotplug and cpu hotplug, and to block native drivers loaded,
@@ -275,7 +269,6 @@ config XEN_STUB
 config XEN_ACPI_HOTPLUG_MEMORY
 	tristate "Xen ACPI memory hotplug"
 	depends on XEN_DOM0 && XEN_STUB && ACPI
-	default n
 	help
 	  This is Xen ACPI memory hotplug.
 
@@ -287,7 +280,6 @@ config XEN_ACPI_HOTPLUG_CPU
 	tristate "Xen ACPI cpu hotplug"
 	depends on XEN_DOM0 && XEN_STUB && ACPI
 	select ACPI_CONTAINER
-	default n
 	help
 	  Xen ACPI cpu enumerating and hotplugging
 
@@ -316,7 +308,6 @@ config XEN_ACPI_PROCESSOR
 config XEN_MCE_LOG
 	bool "Xen platform mcelog"
 	depends on XEN_DOM0 && X86_64 && X86_MCE
-	default n
 	help
 	  Allow kernel fetching MCE error from Xen platform and
 	  converting it into Linux mcelog format for mcelog tools

drivers/xen/xen-balloon.c

@@ -76,12 +76,15 @@ static void watch_target(struct xenbus_watch *watch,
 
 	if (!watch_fired) {
 		watch_fired = true;
-		err = xenbus_scanf(XBT_NIL, "memory", "static-max", "%llu",
+
-				   &static_max);
+		if ((xenbus_scanf(XBT_NIL, "memory", "static-max",
-		if (err != 1)
+				  "%llu", &static_max) == 1) ||
-			static_max = new_target;
+		    (xenbus_scanf(XBT_NIL, "memory", "memory_static_max",
-		else
+				  "%llu", &static_max) == 1))
 			static_max >>= PAGE_SHIFT - 10;
+		else
+			static_max = new_target;
+
 		target_diff = (xen_pv_domain() || xen_initial_domain()) ? 0
 				: static_max - balloon_stats.target_pages;
 	}

drivers/xen/xenbus/xenbus_client.c

@@ -278,10 +278,8 @@ static void xenbus_va_dev_error(struct xenbus_device *dev, int err,
 	dev_err(&dev->dev, "%s\n", printf_buffer);
 
 	path_buffer = kasprintf(GFP_KERNEL, "error/%s", dev->nodename);
-	if (!path_buffer ||
+	if (path_buffer)
-	    xenbus_write(XBT_NIL, path_buffer, "error", printf_buffer))
+		xenbus_write(XBT_NIL, path_buffer, "error", printf_buffer);
-		dev_err(&dev->dev, "failed to write error node for %s (%s)\n",
-			dev->nodename, printf_buffer);
 
 	kfree(printf_buffer);
 	kfree(path_buffer);