Re: [Xen-devel] [PATCH RFC 0/3] VMX: fix interaction of Viridian emulation with advanced features

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

George Dunlap wrote on 2013-06-22:
> On 21/06/13 14:57, Jan Beulich wrote:
>>>>> On 21.06.13 at 12:31, "Jan Beulich" <JBeulich@xxxxxxxx> wrote:
>>> 1: VMX: fix interaction of APIC-V and Viridian emulation
>>> 2: VMX/Viridian: suppress MSR-based APIC suggestion when having APIC-V
>>> 3: Viridian: populate CPUID leaf 6
>>> 
>>> The concepts patch 1 bases upon have been tested to fix the Win2008
>>> boot hang previously reported, but the specific patch here so far hasn't
>>> got validated. Additionally I will also want to know whether patch 2
>>> alone would also suffice to address the problem (it should in theory, but
>>> so far it was only tested when at the same time also not setting
>>> CPUID3A_MSR_APIC_ACCESS) - if it does, that might be a candidate
>>> to still go into 4.3.
>> George,
>> 
>> the tests meanwhile completed successfully, i.e. both patch 1
>> and patch 2 alone address the issue. I'd therefore like to propose
>> patch 2 as an immediate non-intrusive fix for 4.3, whereas I'd be
>> fine deferring the first one until after 4.3; deferring the third one
>> seems obvious as it is not fixing any known bug.
>> 
>> Paul, would you btw feel like reviewing/acking patches 2 and 3?
> 
> Just to clarify -- #1 makes it so that the software EOI does what the
> hardware EOI would do if it were used instead?
Correct!

> It's a bit hard to tell which one of 1 or 2 is the lowest risk from a
> release perspective -- my instinct is to go with #1 (assuming I've
> understood it correctly), as it relies on expected behavior of the
> hardware, not on expected behavior of Windows.  But I think whichever
> you think is best is fine with me, as long as you get an Ack from Paul
> for #2.
I think both #1 and #2 are necessary. We cannot expect the OS always follows 
the rule.

Best regards,
Yang


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