Here is the alternative patch you expected.
ACPI: re-enable mwait for xen cpuidle
Xen hypervisor doesn't export mwait feature to dom0, but latest Linux kernel
start to check this feature while initializing _PDC object. Modify xen_cpuid to
re-enable mwait for xen cpuidle.
Signed-off-by: Wei Gang <gang.wei@xxxxxxxxx>
diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index c3e8bff..565244f 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -189,6 +189,8 @@ static void xen_cpuid(unsigned int *ax, unsigned int *bx,
unsigned maskebx = ~0;
unsigned maskecx = ~0;
unsigned maskedx = ~0;
+ unsigned setecx = 0;
+ unsigned setedx = 0;
/*
* Mask out inconvenient features, to try and disable as many
@@ -198,6 +200,12 @@ static void xen_cpuid(unsigned int *ax, unsigned int *bx,
case 0x1:
maskecx = cpuid_leaf1_ecx_mask;
maskedx = cpuid_leaf1_edx_mask;
+ setecx = 1 << (X86_FEATURE_MWAIT % 32);
+ break;
+
+ case 0x5: /* MWAIT INFO */
+ setecx = 0x3; /* EXTENSIONS_SUPPORTED | INTERRUPT_BREAK */
+ setedx = ~0;
break;
case 0xb:
@@ -220,6 +228,8 @@ static void xen_cpuid(unsigned int *ax, unsigned int *bx,
*bx &= maskebx;
*cx &= maskecx;
*dx &= maskedx;
+ *cx |= setecx;
+ *dx |= setedx;
}
static __init void xen_init_cpuid_mask(void)
On Friday, 2010-4-2 2:33 PM, Wei, Gang wrote:
> On Friday, 2010-4-2 1:41 PM, Jeremy Fitzhardinge wrote:
>> On 04/01/2010 07:38 PM, Wei, Gang wrote:
>>> I suggest including this patch in Xen 4.0 release. It is quite
>>> straightforward, and make sure the better and widely equipped cpu
>>> idle entry method MWAIT is used by xen if available.
>>>
>>> BTW, can we consider re-open MWAIT freature for dom0 in xen
>>> hypervisor? We can discuss it post 4.0.
>>>
>>> Jimmy
>>>
>>> ACPI: re-enable mwait for xen cpuidle
>>>
>>> Xen hypervisor doesn't export mwait feature to dom0, but latest
>>> Linux kernel start to check this feature while initializing _PDC
>>> object. Bypass such check in pv-ops case to re-enable mwait for xen
>>> cpuidle.
>>>
>>
>> Why not just set or clear the MWAIT feature flag in xen_cpuid?
>
> Yes, you pointed out another approach in dom0 side which has similar
> effect as re-open MWAIT feature for dom0 in xen. I am not sure
> whether exposing the MWAIT feature to whole dom0 kernel is ok. My way
> is just to narrow the impact.
>
> Jimmy
re-enable-mwait_pv-ops-dom0-v2.patch
Description: re-enable-mwait_pv-ops-dom0-v2.patch
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