Re: Kernel 2.6.39+ hangs when running as HVM guest under Xen

[Stefan Bader <stefan.bader@canonical.com>]

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So after a bit more help from Stefano, a fix for that could be this one:

>From 8e6c2f27782859b657faef508c6b56c2068af533 Mon Sep 17 00:00:00 2001
From: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Date: Wed, 17 Aug 2011 10:10:59 +0200
Subject: [PATCH] UBUNTU: (upstream) xen: Do not enable PV IPIs when vector
callback not present

Fix regression for HVM case on older (<4.1.1) hypervisors caused by

  commit 99bbb3a84a99cd04ab16b998b20f01a72cfa9f4f
  Author: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
  Date:   Thu Dec 2 17:55:10 2010 +0000

    xen: PV on HVM: support PV spinlocks and IPIs

This change replaced the SMP operations with event based handlers without
taking into account that this only works when the hypervisor supports
callback vectors. This causes unexplainable hangs early on boot for
HVM guests with more than one CPU.

BugLink: http://bugs.launchpad.net/bugs/791850

Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

---
 arch/x86/xen/smp.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index b4533a8..e79dbb9 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -521,8 +521,6 @@ static void __init xen_hvm_smp_prepare_cpus(unsigned int
max_cpus)
        native_smp_prepare_cpus(max_cpus);
        WARN_ON(xen_smp_intr_init(0));

-       if (!xen_have_vector_callback)
-               return;
        xen_init_lock_cpu(0);
        xen_init_spinlocks();
 }
@@ -546,6 +544,8 @@ static void xen_hvm_cpu_die(unsigned int cpu)
 void __init xen_hvm_smp_init(void)
 {
+       if (!xen_have_vector_callback)
+               return;
        smp_ops.smp_prepare_cpus = xen_hvm_smp_prepare_cpus;
        smp_ops.smp_send_reschedule = xen_smp_send_reschedule;
        smp_ops.cpu_up = xen_hvm_cpu_up;
-- 
1.7.4.1

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>From 8e6c2f27782859b657faef508c6b56c2068af533 Mon Sep 17 00:00:00 2001
From: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
Date: Wed, 17 Aug 2011 10:10:59 +0200
Subject: [PATCH] UBUNTU: (upstream) xen: Do not enable PV IPIs when vector callback not present

Fix regression for HVM case on older (<4.1.1) hypervisors caused by

  commit 99bbb3a84a99cd04ab16b998b20f01a72cfa9f4f
  Author: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
  Date:   Thu Dec 2 17:55:10 2010 +0000

    xen: PV on HVM: support PV spinlocks and IPIs

This change replaced the SMP operations with event based handlers without
taking into account that this only works when the hypervisor supports
callback vectors. This causes unexplainable hangs early on boot for
HVM guests with more than one CPU.

BugLink: http://bugs.launchpad.net/bugs/791850

Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
---
 arch/x86/xen/smp.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
index b4533a8..e79dbb9 100644
--- a/arch/x86/xen/smp.c
+++ b/arch/x86/xen/smp.c
@@ -521,8 +521,6 @@ static void __init xen_hvm_smp_prepare_cpus(unsigned int max_cpus)
 	native_smp_prepare_cpus(max_cpus);
 	WARN_ON(xen_smp_intr_init(0));
 
-	if (!xen_have_vector_callback)
-		return;
 	xen_init_lock_cpu(0);
 	xen_init_spinlocks();
 }
@@ -546,6 +544,8 @@ static void xen_hvm_cpu_die(unsigned int cpu)
 
 void __init xen_hvm_smp_init(void)
 {
+	if (!xen_have_vector_callback)
+		return;
 	smp_ops.smp_prepare_cpus = xen_hvm_smp_prepare_cpus;
 	smp_ops.smp_send_reschedule = xen_smp_send_reschedule;
 	smp_ops.cpu_up = xen_hvm_cpu_up;
-- 
1.7.4.1


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