[PATCH RFC V9 6/19] xen/pvticketlocks: Add xen_nopvspin parameter to disable xen pv ticketlocks

[Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>]

xen/pvticketlocks: Add xen_nopvspin parameter to disable xen pv ticketlocks

From: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Raghavendra K T <raghavendra.kt@linux.vnet.ibm.com>
---
 arch/x86/xen/spinlock.c |   14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/arch/x86/xen/spinlock.c b/arch/x86/xen/spinlock.c
index 860e190..3de6805 100644
--- a/arch/x86/xen/spinlock.c
+++ b/arch/x86/xen/spinlock.c
@@ -238,6 +238,8 @@ void xen_uninit_lock_cpu(int cpu)
 	per_cpu(lock_kicker_irq, cpu) = -1;
 }
 
+static bool xen_pvspin __initdata = true;
+
 void __init xen_init_spinlocks(void)
 {
 	/*
@@ -247,10 +249,22 @@ void __init xen_init_spinlocks(void)
 	if (xen_hvm_domain())
 		return;
 
+	if (!xen_pvspin) {
+		printk(KERN_DEBUG "xen: PV spinlocks disabled\n");
+		return;
+	}
+
 	pv_lock_ops.lock_spinning = xen_lock_spinning;
 	pv_lock_ops.unlock_kick = xen_unlock_kick;
 }
 
+static __init int xen_parse_nopvspin(char *arg)
+{
+	xen_pvspin = false;
+	return 0;
+}
+early_param("xen_nopvspin", xen_parse_nopvspin);
+
 #ifdef CONFIG_XEN_DEBUG_FS
 
 static struct dentry *d_spin_debug;