[RFC PATCH V2 8/8] xen: register 3-level event channel

[Wei Liu <wei.liu2@citrix.com>]

The 3-level event channel is registered in
 a) xen_init_IRQ(), when the guest is fresh started;
 b) xen_vcpu_restore(), when the guest is restored.

If registration fails, the kernel will fall back to 2-level event channel.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
---
 arch/x86/xen/enlighten.c |   12 ++++++++++++
 drivers/xen/events.c     |   11 ++++++++++-
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index bc893e7..25481b1 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -43,6 +43,7 @@
 #include <xen/hvm.h>
 #include <xen/hvc-console.h>
 #include <xen/acpi.h>
+#include <xen/events.h>
 
 #include <asm/paravirt.h>
 #include <asm/apic.h>
@@ -177,6 +178,7 @@ static void xen_vcpu_setup(int cpu)
 void xen_vcpu_restore(void)
 {
 	int cpu;
+	int rc;
 
 	for_each_possible_cpu(cpu) {
 		bool other_cpu = (cpu != smp_processor_id());
@@ -195,6 +197,16 @@ void xen_vcpu_restore(void)
 		    HYPERVISOR_vcpu_op(VCPUOP_up, cpu, NULL))
 			BUG();
 	}
+
+	if (!(rc = xen_event_channel_register_nlevel(3))) {
+		printk(KERN_INFO "Register 3-level event channel succeeded.\n");
+		xen_set_event_channel_nlevel(3);
+	} else {
+		printk(KERN_INFO "Register 3-level event channel failed with %d.\n"
+		       "Fall back to default 2-level event channel.\n",
+		       rc);
+		xen_set_event_channel_nlevel(2);
+	}
 }
 
 static void __init xen_banner(void)
diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 76ff48c..45159d9 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -2291,7 +2291,16 @@ void __init xen_init_IRQ(void)
 	int i, rc;
 	int cpu;
 
-	/* Setup 2-level event channel */
+	if (!(rc = xen_event_channel_register_3level())) {
+		printk(KERN_INFO "Register 3-level event channel succeeded.\n");
+		xen_set_event_channel_nlevel(3);
+	} else {
+		printk(KERN_INFO "Register 3-level event channel failed with %d.\n"
+		       "Fall back to default 2-level event channel.\n",
+		       rc);
+		xen_set_event_channel_nlevel(2);
+	}
+
 	evtchn_to_irq = kcalloc(nr_event_channels, sizeof(*evtchn_to_irq),
 				GFP_KERNEL);
 	BUG_ON(!evtchn_to_irq);
-- 
1.7.10.4