Re: [Xen-devel] [PATCH]ACPI: re-enable mwait for xen cpuidle

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

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?

    J

> Signed-off-by: Wei Gang<gang.wei@xxxxxxxxx>
> Signed-off-by: Yu Ke<ke.yu@xxxxxxxxx>
>
> diff --git a/arch/x86/kernel/acpi/processor.c b/arch/x86/kernel/acpi/processor.c
> index 8c9526d..d88866c 100644
> --- a/arch/x86/kernel/acpi/processor.c
> +++ b/arch/x86/kernel/acpi/processor.c
> @@ -60,7 +60,7 @@ static void init_intel_pdc(struct acpi_processor *pr, struct 
> cpuinfo_x86 *c)
>         /*
>          * If mwait/monitor is unsupported, C2/C3_FFH will be disabled
>          */
> -       if (!cpu_has(c, X86_FEATURE_MWAIT))
> +       if (!cpu_has(c, X86_FEATURE_MWAIT)&&  !xen_initial_domain())
>                 buf[2]&= ~(ACPI_PDC_C_C2C3_FFH);
>
>         obj->type = ACPI_TYPE_BUFFER;
> diff --git a/drivers/acpi/processor_idle.c b/drivers/acpi/processor_idle.c
> index 22baf4c..0a81637 100644
> --- a/drivers/acpi/processor_idle.c
> +++ b/drivers/acpi/processor_idle.c
> @@ -419,7 +419,8 @@ static int acpi_processor_get_power_info_cst(struct 
> acpi_processor *pr)
>                                 cx.entry_method = ACPI_CSTATE_HALT;
>                                 snprintf(cx.desc, ACPI_CX_DESC_LEN, "ACPI HLT");
>                         } else {
> -                               continue;
> +                               if (!xen_initial_domain())
> +                                       continue;
>                         }
>                         if (cx.type == ACPI_STATE_C1&&
>                                         (idle_halt || idle_nomwait)) {
>
>
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>    

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