From: Talons Lee <xin...@citrix.com>
Commit e657fcc clears cpu x2apic capability bit instead of using fake
cpuid value. However, with cpuid x2apic bit on, xen_read_msr_safe() will
not clear the EXTD bit, which leads to uncessary msr write trying to
disable x2apic in __x2apic_disable(). So restore the fake x2apic value.
Signed-off-by: Talons Lee <xin...@citrix.com>
---
CC: Igor Druzhinin <igor.druzhi...@citrix.com>
CC: Sergey Dyasli <sergey.dya...@citrix.com>
CC: Andrew Cooper <andrew.coop...@citrix.com>
CC: Juergen Gross <jgr...@suse.com>
---
arch/x86/xen/enlighten_pv.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 4b20082..156c408 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -165,12 +165,17 @@ static void xen_cpuid(unsigned int *ax, unsigned int *bx,
unsigned int *cx, unsigned int *dx)
{
unsigned maskebx = ~0;
+ unsigned maskecx = ~0;
/*
* Mask out inconvenient features, to try and disable as many
* unsupported kernel subsystems as possible.
*/
switch (*ax) {
+ case 1:
+ maskecx &= ~(1 << (X86_FEATURE_X2APIC % 32));
+ break;
+
case CPUID_MWAIT_LEAF:
/* Synthesize the values.. */
*ax = 0;
@@ -193,6 +198,7 @@ static void xen_cpuid(unsigned int *ax, unsigned int *bx,
: "0" (*ax), "2" (*cx));
*bx &= maskebx;
+ *cx &= maskecx;
}
STACK_FRAME_NON_STANDARD(xen_cpuid); /* XEN_EMULATE_PREFIX */
--
1.8.3.1
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