Xen devel - Sep 2006 - [PATCH] hvm: clear vmxe if vmxoff

hvm: clear vmxe if vmxoff

The current Xen code keeps X86_CR4_VMXE set even if VMXON has not been 
executed. The stop_vmx() code assumes that it is possible to call VMXOFF
if X86_CR4_VMXE is set which is not always true. Calling VMXOFF without 
VMXON results in an illegal opcode trap, and to avoid this condition this 
patch makes sure that X86_CR4_VMXE is only set when VMXON has been called.

Tested using x86_32 on a Pentium D 930.

Signed-Off-By: Magnus Damm <magnus@valinux.co.jp>

--- 0001/xen/arch/x86/hvm/vmx/vmx.c
+++ work/xen/arch/x86/hvm/vmx/vmx.c	2006-09-29 14:49:55.000000000 +0900
@@ -485,8 +485,10 @@ static void vmx_ctxt_switch_to(struct vc
 
 static void stop_vmx(void)
 {
-    if (read_cr4() & X86_CR4_VMXE)
+    if (read_cr4() & X86_CR4_VMXE) {
         __vmxoff();
+        clear_in_cr4(X86_CR4_VMXE);
+    }
 }
 
 void vmx_migrate_timers(struct vcpu *v)
@@ -806,12 +808,14 @@ int start_vmx(void)
 
     if ( (vmcs = vmx_alloc_host_vmcs()) == NULL )
     {
+        clear_in_cr4(X86_CR4_VMXE);
         printk("Failed to allocate host VMCS\n");
         return 0;
     }
 
     if ( __vmxon(virt_to_maddr(vmcs)) )
     {
+        clear_in_cr4(X86_CR4_VMXE);
         printk("VMXON failed\n");
         vmx_free_host_vmcs(vmcs);
         return 0;

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hvm: disable hvm on smp

With Intel VT, VMXOFF needs to be executed before halting the CPU. Without 
this fix Xen or Linux is unable to start up the CPU after a kexec reboot.

Tested using x86_32 on a Pentium D 930.

Signed-Off-By: Magnus Damm <magnus@valinux.co.jp>

--- 0001/xen/arch/x86/smp.c
+++ work/xen/arch/x86/smp.c	2006-09-29 14:47:34.000000000 +0900
@@ -21,6 +21,7 @@
 #include <asm/smpboot.h>
 #include <asm/hardirq.h>
 #include <asm/ipi.h>
+#include <asm/hvm/hvm.h>
 #include <mach_apic.h>
 
 /*
@@ -306,6 +307,7 @@ static void stop_this_cpu (void *dummy)
 
     local_irq_disable();
     disable_local_APIC();
+    hvm_disable();
 
     for ( ; ; )
         __asm__ __volatile__ ( "hlt" );

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