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

3 files changed, 17 insertions, 22 deletions

diff --git a/arch/x86/xen/platform-pci-unplug.c b/arch/x86/xen/platform-pci-unplug.c
index 66ab96a4e2b3..96d7f7d39cb9 100644
--- a/arch/x86/xen/platform-pci-unplug.c
+++ b/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;
diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c
index 23f6793af88a..441c88262169 100644
--- a/arch/x86/xen/spinlock.c
+++ b/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 */
-	xen_clear_irq_pending(irq);
-	barrier();
-
-	/*
-	 * We check the byte value after clearing pending IRQ to make sure
-	 * that we won't miss a wakeup event because of the clearing.
-	 *
-	 * The sync_clear_bit() call in xen_clear_irq_pending() is atomic.
-	 * So it is effectively a memory barrier for x86.
-	 */
-	if (READ_ONCE(*byte) != val)
-		return;
+	/* Guard against reentry. */
+	local_irq_save(flags);
 
-	/*
-	 * If an interrupt happens here, it will leave the wakeup irq
-	 * pending, which will cause xen_poll_irq() to return
-	 * immediately.
-	 */
+	/* If irq pending already clear it. */
+	if (xen_test_irq_pending(irq)) {
+		xen_clear_irq_pending(irq);
+	} else if (READ_ONCE(*byte) == val) {
+		/* Block until irq becomes pending (or a spurious wakeup) */
+		xen_poll_irq(irq);
+	}
 
-	/* Block until irq becomes pending (or perhaps a spurious wakeup) */
-	xen_poll_irq(irq);
+	local_irq_restore(flags);
 }
 
 static irqreturn_t dummy_handler(int irq, void *dev_id)
diff --git a/arch/x86/xen/xen-pvh.S b/arch/x86/xen/xen-pvh.S
index b0e471506cd8..1f8825bbaffb 100644
--- a/arch/x86/xen/xen-pvh.S
+++ b/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,