lguest: restrict CPUID to avoid perf counter wrmsr

Avoid the following:
[    0.012093] WARNING: at arch/x86/kernel/apic/apic.c:249 native_apic_write_dummy+0x2f/0x40()

Rather than chase each new cpuid-detected feature, just lie about the highest
valid CPUID so this code is never run.

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

1 files changed, 5 insertions, 0 deletions

diff --git a/arch/x86/lguest/boot.c b/arch/x86/lguest/boot.c
index 0188fd37b6c0..f2bf1f73d468 100644
--- a/arch/x86/lguest/boot.c
+++ b/arch/x86/lguest/boot.c
@@ -379,6 +379,11 @@ static void lguest_cpuid(unsigned int *ax, unsigned int *bx,
 
         native_cpuid(ax, bx, cx, dx);
         switch (function) {
+        case 0: /* ID and highest CPUID.  Futureproof a little by sticking to
+                 * older ones. */
+                if (*ax > 5)
+                        *ax = 5;
+                break;
         case 1: /* Basic feature request. */
                 /* We only allow kernel to see SSE3, CMPXCHG16B and SSSE3 */
                 *cx &= 0x00002201;