Re: [Xen-devel] [PATCH v5] x86/AMD: Add support for AMD's OSVW feature in guests

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 06.02.12 at 18:47, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> wrote:
> On Mon, Feb 06, 2012 at 06:39:25PM +0100, Boris Ostrovsky wrote:
>> # HG changeset patch
>> # User Boris Ostrovsky <boris.ostrovsky@xxxxxxx>
>> # Date 1328549858 -3600
>> # Node ID 3cf8ffd0ab883dd09f943f4d8fb50f5cc1f04cd5
>> # Parent  e2722b24dc0962de37215320b05d1bb7c4c42864
>> x86/AMD: Add support for AMD's OSVW feature in guests.
>> 
>> In some cases guests should not provide workarounds for errata even when the
>> physical processor is affected. For example, because of erratum 400 on 
> family
>> 10h processors a Linux guest will read an MSR (resulting in VMEXIT) before
>> going to idle in order to avoid getting stuck in a non-C0 state. This is not
> 
> What about fixing the Linux guest to actually not do this? I presume you
> have encountered this with HVM guests - would it be possible to use
> 
> set_pm_idle_to_default(default_idle) in the HVM bootup path, say in 
> 'xen_hvm_guest_init' ??

Are you saying this would work even with CONFIG_XEN not set
(which I doubt, but is a valid case to consider)?

Also, this sort of adjustment is exactly what is being done better
in the hypervisor, as it'll address the problem at hand for all guests,
no matter what kernel (version or kind) they run.

Jan


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