The following commit has been merged in the linux branch: commit 82d6469916c6fcfa345636a49004c9d1753905d1 Author: Jeremy Fitzhardinge jeremy.fitzhardinge@citrix.com Date: Thu Oct 22 16:41:15 2009 -0700

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 __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; }