linux-kernel - Re: [PATCH RESEND 1/1] X86: Handle Hyper-V vmbus interrupts as special hypervisor interrupts

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Date:	Fri, 25 Jan 2013 07:35:04 +0000
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"Olaf Hering" <olaf@...fle.de>, "KY Srinivasan" <kys@...rosoft.com>
Cc:	"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>,
	"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 RESEND 1/1] X86: Handle Hyper-V vmbus interrupts as
 special hypervisor interrupts

>>> On 24.01.13 at 19:59, Olaf Hering <olaf@...fle.de> wrote:
> On Thu, Jan 24, KY Srinivasan wrote:
> 
> 
>> > Question is - considering you stated that this is supported
>> > starting in Win8, doesn't Hyper-V itself announce that
>> > capability in some explicit way?
>> 
>> Thanks Jan. Unfortunately I don't think tis interrupt delivery model
>> is specified via a "feature" bit (I will check with the Windows guys).
>> Perhaps, we can have a Hyper-V specific compilation switch to address
>> the Xen emulation issue.
> 
> Would that really help if both pvops XEN_PVHVM and HYPERV are enabled in
> the config? I assume at this point the access to the DMI data is not yet
> possible.

As just said in another reply - with XEN_PVHVM, there's no problem,
since Xen gets checked for first. There's only a problem when
!XEN_PVHVM, because in that case Hyper-V will be probed for.
And the problem can only get bigger when on top of that the
out-of-tree PV drivers are intended to be used.

Jan

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