Re: [Xen-devel] [PATCH v2] x86: Use deep C states for off-lined CPUs

["Liu, Jinsong" <jinsong.liu@xxxxxxxxx>]

Fine to me.
BTW, seems another patch moving mwait_ptr declaration and related code into 
if(FFH) is slightly better? It's FFH staff anyway.

Thanks,
Jinsong

Boris Ostrovsky wrote:
> # HG changeset patch
> # User Boris Ostrovsky <boris.ostrovsky@xxxxxxx>
> # Date 1330642361 -3600
> # Node ID 99df5c6b2964ceaa73651d7bc02fb1ae820f7691
> # Parent  a7bacdc5449a2f7bb9c35b2a1334b463fe9f29a9
> x86: Use deep C states for off-lined CPUs
> 
> Currently when a core is taken off-line it is placed in C1 state
> (unless MONITOR/MWAIT is used). This patch allows a core to go to
> deeper C states resulting in significantly higher power savings.
> 
> Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxx>
> 
> diff -r a7bacdc5449a -r 99df5c6b2964 xen/arch/x86/acpi/cpu_idle.c
> --- a/xen/arch/x86/acpi/cpu_idle.c    Mon Feb 27 17:05:18 2012 +0000
> +++ b/xen/arch/x86/acpi/cpu_idle.c    Thu Mar 01 23:52:41 2012 +0100
> @@ -566,6 +566,7 @@ static void acpi_dead_idle(void)
>      struct acpi_processor_power *power;
>      struct acpi_processor_cx *cx;
>      void *mwait_ptr;
> +    struct cpuinfo_x86 *c = &current_cpu_data;
> 
>      if ( (power = processor_powers[smp_processor_id()]) == NULL )
>          goto default_halt;
> @@ -601,6 +602,23 @@ static void acpi_dead_idle(void)
>              mb();
>              __mwait(cx->address, 0);
>          }
> +    }
> +    else if ( c->x86_vendor == X86_VENDOR_AMD &&
> +              cx->entry_method == ACPI_CSTATE_EM_SYSIO )
> +    {
> +        /* Intel prefers not to use SYSIO */
> +
> +        /* Avoid references to shared data after the cache flush */
> +        u32 address = cx->address;
> +        u32 pmtmr_ioport_local = pmtmr_ioport;
> +
> +        wbinvd();
> +
> +        while ( 1 )
> +        {
> +            inb(address);
> +            inl(pmtmr_ioport_local);
> +        }
>      }
> 
>  default_halt:


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel