Re: [Xen-devel] Xen 4.3 development update

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> 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
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).

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


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