xen: mask extended topology info in cpuid
A Xen guest never needs to know about extended topology, and knowing
would just confuse it.
This patch just zeros ebx in leaf 0xb which indicates no topology info,
preventing a crash under Xen on cpus which support this leaf.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
Cc: Stable Kernel <stable@kernel.org>
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 23a4d80..dfbf70e 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -178,6 +178,7 @@
static void xen_cpuid(unsigned int *ax, unsigned int *bx,
unsigned int *cx, unsigned int *dx)
{
+ unsigned maskebx = ~0;
unsigned maskecx = ~0;
unsigned maskedx = ~0;
@@ -185,9 +186,16 @@
* Mask out inconvenient features, to try and disable as many
* unsupported kernel subsystems as possible.
*/
- if (*ax == 1) {
+ switch (*ax) {
+ case 1:
maskecx = cpuid_leaf1_ecx_mask;
maskedx = cpuid_leaf1_edx_mask;
+ break;
+
+ case 0xb:
+ /* Suppress extended topology stuff */
+ maskebx = 0;
+ break;
}
asm(XEN_EMULATE_PREFIX "cpuid"
@@ -197,6 +205,7 @@
"=d" (*dx)
: "0" (*ax), "2" (*cx));
+ *bx &= maskebx;
*cx &= maskecx;
*dx &= maskedx;
}