linux-kernel - Re: [PATCH 2/3] X86: Add a check to catch Xen emulation of Hyper-V

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Date:	Wed, 17 Apr 2013 15:09:33 +0100
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	"olaf@...fle.de" <olaf@...fle.de>, "bp@...en8.de" <bp@...en8.de>,
	"apw@...onical.com" <apw@...onical.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
	"gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
	"KY Srinivasan" <kys@...rosoft.com>,
	"jasowang@...hat.com" <jasowang@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"hpa@...or.com" <hpa@...or.com>
Subject: Re: [PATCH 2/3] X86: Add a check to catch Xen emulation of
 Hyper-V

>>> On 17.04.13 at 15:01, "Michael S. Tsirkin" <mst@...hat.com> wrote:
> On Wed, Apr 17, 2013 at 02:52:42PM +0100, Jan Beulich wrote:
>> >>> On 17.04.13 at 15:20, KY Srinivasan <kys@...rosoft.com> wrote:
>> > If I recall correctly, the issue here was that Xen was enabling Hyper-V 
>> > emulation un-conditionally even for Linux guests.
>> 
>> To make this a little more precise - Xen is doing so only when the
>> guest config tells it to.
> 
> So it's something explicitly requested for this guest?  Then I don't
> understand why does not make sense to override it in guest.

Iirc it was/is XenServer which enable Hyper-V emulation for all HVM
guests, which clearly is the wrong thing. I was personally also not
really in agreement with the override in the kernel, but it was
decided to do it that way at that point in time. As a consequence,
I don't object this to be reverted.

Jan

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