linux-kernel - Re: Xenner design and kvm msr handling

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Date:	Tue, 21 Apr 2009 18:00:45 +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: Xenner design and kvm msr handling

On 04/21/09 15:33, Avi Kivity wrote:
> Gerd Hoffmann wrote:
>> Not sure, have to dig into the xen code to figure.
>>
>> Could be xen doesn't remember the page in the first place. They might
>> let the illegal instruction fault handler patch the opcode. At least I
>> vaguely remember some discussions about that.

Xen does a simple msr-triggered memcpy() as well, without keeping track 
of the page.  On a quick glimpse I can't find a opcode patching place 
either.  Hmm.

>> Could be there isn't a interface to forgot the page. "reboot" in xen
>> land is "destroy guest, restart it".
>
> How do you unload a driver then?

The linux module (xen-platform-pci) has no module_exit() ...

cheers,
   Gerd
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