From: Eduardo Habkost <ehabkost@redhat.com>
Date: Tue, 7 Jul 2009 18:11:22 -0300
Subject: [x86_64] disable VMX and SVM on machine_crash_shutdown
Message-id: 1247001082-20497-7-git-send-email-ehabkost@redhat.com
O-Subject: [RHEL-5.4 PATCH 6/6] x86_64: disable VMX and SVM on machine_crash_shutdown() (v2)
Bugzilla: 507483

This is done only on x86_64 and not on i386 because that's the only
architecture where we support KVM.

Backport of upstream commit:

 commit 2340b62f77c782c305e6ae7748675a638436d1ef
 Author: Eduardo Habkost <ehabkost@redhat.com>
 Date:   Mon Nov 17 19:03:23 2008 -0200

    kdump: forcibly disable VMX and SVM on machine_crash_shutdown()

    We need to disable virtualization extensions on all CPUs before booting
    the kdump kernel, otherwise the kdump kernel booting will fail, and
    rebooting after the kdump kernel did its task may also fail.

    We do it using cpu_emergency_vmxoff() and cpu_emergency_svm_disable(),
    that should always work, because those functions check if the CPUs
    support SVM or VMX before doing their tasks.

    Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
    Signed-off-by: Avi Kivity <avi@redhat.com>

Changelog:
 - v2: include asm/virtext.h only if !CONFIG_XEN

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>

diff --git a/arch/x86_64/kernel/crash.c b/arch/x86_64/kernel/crash.c
index 7f7792b..d02e355 100644
--- a/arch/x86_64/kernel/crash.c
+++ b/arch/x86_64/kernel/crash.c
@@ -25,6 +25,10 @@
 #include <asm/hw_irq.h>
 #include <asm/mach_apic.h>
 
+#ifndef CONFIG_XEN
+#include <asm/virtext.h>
+#endif
+
 /* This keeps a track of which one is crashing cpu. */
 static int crashing_cpu;
 
@@ -109,6 +113,16 @@ static int crash_nmi_callback(struct pt_regs *regs, int cpu)
 	local_irq_disable();
 
 	crash_save_this_cpu(regs, cpu);
+
+	/* Disable VMX or SVM if needed.
+	 *
+	 * We need to disable virtualization on all CPUs.
+	 * Having VMX or SVM enabled on any CPU may break rebooting
+	 * after the kdump kernel has finished its task.
+	 */
+	cpu_emergency_vmxoff();
+	cpu_emergency_svm_disable();
+
 	disable_local_APIC();
 	atomic_dec(&waiting_for_crash_ipi);
 	/* Assume hlt works */
@@ -181,6 +195,13 @@ void machine_crash_shutdown(struct pt_regs *regs)
 #ifndef CONFIG_XEN
 	nmi_shootdown_cpus();
 
+	/* Booting kdump kernel with VMX or SVM enabled won't work,
+	 * because (among other limitations) we can't disable paging
+	 * with the virt flags.
+	 */
+	cpu_emergency_vmxoff();
+	cpu_emergency_svm_disable();
+
 	if(cpu_has_apic)
 		 disable_local_APIC();