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Subject[PATCH] xen-dom0: only selectively disable cpu features
Date
Dom0 kernels actually want most of the CPU features to be enabled.
Some, like MCA/MCE, are still handled by Xen itself.

We leave APIC enabled even though we don't really have a functional
local apic so that the ACPI code will parse the corresponding tables
properly.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
---
arch/x86/xen/enlighten.c | 21 +++++++++++++--------
1 files changed, 13 insertions(+), 8 deletions(-)
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index d5fc434..468aa23 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -171,18 +171,23 @@ static void __init xen_banner(void)
static void xen_cpuid(unsigned int *ax, unsigned int *bx,
unsigned int *cx, unsigned int *dx)
{
- unsigned maskedx = ~0;
+ unsigned maskedx = 0;

/*
* Mask out inconvenient features, to try and disable as many
* unsupported kernel subsystems as possible.
*/
- if (*ax == 1)
- maskedx = ~((1 << X86_FEATURE_APIC) | /* disable APIC */
- (1 << X86_FEATURE_ACPI) | /* disable ACPI */
- (1 << X86_FEATURE_MCE) | /* disable MCE */
- (1 << X86_FEATURE_MCA) | /* disable MCA */
- (1 << X86_FEATURE_ACC)); /* thermal monitoring */
+ if (*ax == 1) {
+ maskedx =
+ (1 << X86_FEATURE_MCE) | /* disable MCE */
+ (1 << X86_FEATURE_MCA) | /* disable MCA */
+ (1 << X86_FEATURE_ACC); /* thermal monitoring */
+
+ if (!xen_initial_domain())
+ maskedx |=
+ (1 << X86_FEATURE_APIC) | /* disable local APIC */
+ (1 << X86_FEATURE_ACPI); /* disable ACPI */
+ }

asm(XEN_EMULATE_PREFIX "cpuid"
: "=a" (*ax),
@@ -190,7 +195,7 @@ static void xen_cpuid(unsigned int *ax, unsigned int *bx,
"=c" (*cx),
"=d" (*dx)
: "0" (*ax), "2" (*cx));
- *dx &= maskedx;
+ *dx &= ~maskedx;
}

static void xen_set_debugreg(int reg, unsigned long val)
--
1.6.0.6


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