Re: [Xen-devel] Xen 4.3 development update

["Zhang, Yang Z" <yang.z.zhang@xxxxxxxxx>]

Jan Beulich wrote on 2013-06-20:
>>>> On 17.06.13 at 13:13, "Jan Beulich" <JBeulich@xxxxxxxx> wrote:
>>>>> On 17.06.13 at 12:58, George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
> wrote:
>>> * Win2k8 fails install on many IvyBridge EP systems
>>>> Not reproducible by Intel
>>>> Reproducible on 4.2
>> 
>> Reproducible only on 4.2 with APIC virtualization commits backported.
>> So this is a regression due to new functionality (which to date cannot
>> be worked around).
> 
> Update: This is a bad interaction between Viridian mode and APIC-V.
> Disabling either makes things work again. Yang narrowed this down
> to the EOI handling, and created a non-postable patch that deals
> with the issue (non-postable because it does things in ways only
> suitable for temporary testing). I do think, though, that this isn't the
> way to go anyway - instead we likely will want to suppress Windows
> using the APIC related MSRs when APIC register virtualization is in
> use. Yang seems to agree with this, but this approach wasn't tested
Just do a testing and it is working to not set CPUID3A_MSR_APIC_ACCESS and 
CPUID4A_MSR_BASED_APIC.

> yet (partly because for it to be complete we'd also want to
> populate Viridian CPUID leaf 6, but the APIC related bit there is
> insufficiently specified, so we first need to find out from MS when
> exactly this bit is supposed to get set).
I think CPUID leaf 6 just indicate which hardware feature is used by 
hypervisor. It should have nothing to do with this issue. We can consider it 
separately. 

> 
> In any case, with the workaround of disabling Viridian support now
> known, I guess we can indeed defer fixing this until 4.3.1.
> 
> Jan


Best regards,
Yang


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