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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>
This commit is contained in:
Jeremy Fitzhardinge 2009-10-22 16:41:15 -07:00
parent 7825cf10e3
commit 82d6469916
1 changed files with 10 additions and 1 deletions
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11
arch/x86/xen/enlighten.c
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@ -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;
}