[RFC][PATCH 07/10] xen/hybrid: Add PV timer support

[Sheng Yang <sheng@linux.intel.com>]

If we have event channel, we can use VIRQ_TIMER to deliver timer interrupt,
otherwise we would reuse IRQ0.

Signed-off-by: Sheng Yang <sheng@linux.intel.com>
---
 arch/x86/xen/enlighten.c |   14 ++++++++++++++
 arch/x86/xen/time.c      |   18 +++++++++++++++---
 2 files changed, 29 insertions(+), 3 deletions(-)

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index b6751ed..18aba22 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -53,6 +53,8 @@
 #include <asm/tlbflush.h>
 #include <asm/reboot.h>
 
+#include <xen/hvm.h>
+
 #include "xen-ops.h"
 #include "mmu.h"
 #include "multicalls.h"
@@ -1050,6 +1052,9 @@ static void __init xen_hybrid_banner(void)
 	printk(KERN_INFO "Booting hybrid kernel on %s\n", pv_info.name);
 	printk(KERN_INFO "Xen version: %d.%d%s\n",
 	       version >> 16, version & 0xffff, extra.extraversion);
+
+	if (xen_hybrid_timer_enabled())
+		printk(KERN_INFO "Hybrid feature: PV Timer enabled\n");
 }
 
 static int xen_para_available(void)
@@ -1093,6 +1098,10 @@ static int init_hybrid_info(void)
 		return -ENODEV;
 
 	xen_hybrid_status = XEN_HYBRID_ENABLED;
+	if (edx & XEN_CPUID_FEAT2_HYBRID_TIMER) {
+		xen_hybrid_status |= XEN_HYBRID_TIMER_ENABLED;
+		flags |= HVM_HYBRID_TIMER;
+	}
 
 	/* We only support 1 page of hypercall for now */
 	if (pages != 1)
@@ -1149,5 +1158,10 @@ void __init xen_start_hybrid(void)
 	xen_hybrid_init_irq_ops();
 
 	init_shared_info();
+
+	if (xen_hybrid_timer_enabled()) {
+		pv_time_ops = xen_time_ops;
+		pv_apic_ops = xen_apic_ops;
+	}
 }
 
diff --git a/arch/x86/xen/time.c b/arch/x86/xen/time.c
index 0a5aa44..381f135 100644
--- a/arch/x86/xen/time.c
+++ b/arch/x86/xen/time.c
@@ -421,6 +421,13 @@ static irqreturn_t xen_timer_interrupt(int irq, void *dev_id)
 	return ret;
 }
 
+static struct irqaction xen_timer_irq0 = {
+	.handler	= xen_timer_interrupt,
+	.flags		= IRQF_DISABLED | IRQF_IRQPOLL |
+			  IRQF_NOBALANCING | IRQF_TIMER,
+	.name		= "timer"
+};
+
 void xen_setup_timer(int cpu)
 {
 	const char *name;
@@ -433,9 +440,14 @@ void xen_setup_timer(int cpu)
 	if (!name)
 		name = "<timer kasprintf failed>";
 
-	irq = bind_virq_to_irqhandler(VIRQ_TIMER, cpu, xen_timer_interrupt,
-				      IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
-				      name, NULL);
+	if (xen_hybrid_timer_enabled() && !xen_hybrid_evtchn_enabled()) {
+		irq = 0;
+		setup_irq(0, &xen_timer_irq0);
+	} else
+		irq = bind_virq_to_irqhandler(VIRQ_TIMER, cpu,
+				xen_timer_interrupt,
+				IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
+				name, NULL);
 
 	evt = &per_cpu(xen_clock_events, cpu);
 	memcpy(evt, xen_clockevent, sizeof(*evt));
-- 
1.5.4.5