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authorJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>2009-10-22 16:41:15 -0700
committerJeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>2009-11-03 11:09:12 -0800
commit82d6469916c6fcfa345636a49004c9d1753905d1 (patch)
treef4d95a9159234b66d26e4e8ebe661e105929234b
parent7825cf10e31c64ece3cac66fb01a742f1094da51 (diff)
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>
-rw-r--r--arch/x86/xen/enlighten.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 23a4d80fb39e..dfbf70e65860 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -178,6 +178,7 @@ static __read_mostly unsigned int cpuid_leaf1_ecx_mask = ~0;
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 @@ static void xen_cpuid(unsigned int *ax, unsigned int *bx,
* 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 @@ static void xen_cpuid(unsigned int *ax, unsigned int *bx,
"=d" (*dx)
: "0" (*ax), "2" (*cx));
+ *bx &= maskebx;
*cx &= maskecx;
*dx &= maskedx;
}