Re: [Qemu-devel] [4270] bios: disable processor SSDT generation.

[Avi Kivity <avi@qumranet.com>]

Aurelien Jarno wrote:
> Filip Navara a écrit :
>   
>> Under which operating system and in which conditions? Some operating
>>     
>
> Basically on all systems I tried, that is Linux, Windows 2k and Windows
> XP. This happens for both 32- and 64-bits hosts.
>
>   
>> systems I use under QEMU require the processor descriptors and I've
>> been told that certain version of Windows Vista doesn't idle if the
>> processsor descriptors aren't present.
>>     
>
> I am open to a proper fix, but I think that breaking support for most
> guests to support Windows Vista is a serious regression.

kvm has processor descriptor and proper idle for all guests including 
Vista. 

The following commit is probaby needed:

> commit cb98751267c2d79f5674301ccac6c6b5c2e0c6b5
> Author: Igor Lvovsky <igorl@qumranet.com>
> Date:   Sun Aug 19 14:54:08 2007 +0300
>
>     kvm: bios: don't advertise ACPI C2 or C3 support
>
>     The previous patch fix the SMP guest problem, but
>     now UP guest with SMP HAL consume ~50% CPU (it was 2-3% before that
>     with UP HAL).  To fix it we need disable support of C2 and C3 states
>     via FADT.
>
>     Signed-off-by: Igor Lvovsky <igorl@qumranet.com>
>     Signed-off-by: Avi Kivity <avi@qumranet.com>
>

I'd like to properly support C3 and revert that patch, but that can come 
later.

-- 
Any sufficiently difficult bug is indistinguishable from a feature.