linux-kernel - Re: [PATCH] Add MCE support to KVM

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Date:	Mon, 20 Apr 2009 13:23:22 +0200
From:	Gerd Hoffmann <kraxel@...hat.com>
To:	Avi Kivity <avi@...hat.com>
CC:	Anthony Liguori <anthony@...emonkey.ws>,
	Huang Ying <ying.huang@...el.com>,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH] Add MCE support to KVM

On 04/20/09 11:05, Avi Kivity wrote:
> Gerd Hoffmann wrote:
>> On 04/20/09 10:26, Avi Kivity wrote:
>>> Gerd Hoffmann wrote:
>>>> The xen pv-on-hvm drivers use an msr to indicate "please place the
>>>> hypercall page here". Handling that in kernel isn't an option IMHO.
>>>
>>> The contents of the hypercall page are vendor specific. This can be
>>> handled from userspace (though ideally we'd abstract the cpu vendor
>>> away).
>>
>> Well, xenner doesn't do vmcalls, so the page isn't vendor specific.
>
> Well, for true pv (not pv-on-hvm) it wouldn't use the MSR, would it?

Yes, the MSR is used for pv-on-hvm only.

>> It looks different for 32bit / 64bit guests though. And it actually
>> can be multiple pages (with one msr write per page). So the interface
>> for in-kernel handling would be more complex than "here is a hypercall
>> page for you".
>
> To different MSRs, or multiple writes to the same MSR?

Same MSR, multiple writes (page number in the low bits).

cheers,
   Gerd

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