lguest: don't allow KVM-detection cpuid.

Host might be running under KVM, but we shouldn't allow Guest to think it
can use KVM hypercalls (it can't, and it will embarrass itself if it tries).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index 13ee258442ae2b58cb195374c02c1a213f8333ee..f63da5ef217c40deb6af93e0924246fc68f94008 100644 (file)
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -70,6 +70,7 @@
 #include <asm/i387.h>
 #include <asm/stackprotector.h>
 #include <asm/reboot.h>                /* for struct machine_ops */
+#include <asm/kvm_para.h>
 
 /*G:010
  * Welcome to the Guest!
@@ -455,6 +456,15 @@ static void lguest_cpuid(unsigned int *ax, unsigned int *bx,
                *ax &= 0xFFFFF0FF;
                *ax |= 0x00000500;
                break;
+
+       /*
+        * This is used to detect if we're running under KVM.  We might be,
+        * but that's a Host matter, not us.  So say we're not.
+        */
+       case KVM_CPUID_SIGNATURE:
+               *bx = *cx = *dx = 0;
+               break;
+
        /*
         * 0x80000000 returns the highest Extended Function, so we futureproof
         * like we do above by limiting it to known fields.