RE: [Xen-devel] Re: Does Xen also plan to move the back-end driver to the stub domain for HVM?

["Petersson, Mats" <Mats.Petersson@xxxxxxx>]

> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx 
> [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Liang Yang
> Sent: 19 March 2007 19:21
> To: Anthony Liguori
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: Re: [Xen-devel] Re: Does Xen also plan to move the 
> back-end driver to the stub domain for HVM?
> 
> "QEMU has direct access to hardware", does this mean the QEMU 
> device model 
> does not need to communicate with the native device driver 
> which is also 
> sitting in dom0?

No, it needs the Dom0 device driver. 

--
Mats
> 
> 
> ----- Original Message ----- 
> From: "Anthony Liguori" <aliguori@xxxxxxxxxx>
> To: "Liang Yang" <multisyncfe991@xxxxxxxxxxx>
> Cc: <xen-devel@xxxxxxxxxxxxxxxxxxx>
> Sent: Monday, March 19, 2007 11:20 AM
> Subject: [Xen-devel] Re: Does Xen also plan to move the 
> back-end driver to 
> the stub domain for HVM?
> 
> 
> > Liang Yang wrote:
> >> Hi,
> >>
> >> Based on the roadmap on Xen summit, there is a plan to 
> move QEMU and let 
> >> it run on the stub domain to improve HVM performance.
> >
> > Using a stub domain won't improve HVM performance.  It will improve 
> > accountability and scalability but running a single HVM 
> guest shouldn't 
> > see any improvement.
> >
> >> However, comparing with QEMU device model, it will be much 
> easier to move 
> >> BE driver and let it run in stub domain instead of dom0 as 
> BE part is 
> >> running on the kernel space (QEMU is running on user space).
> >
> > Actually, this cannot make performance better since you're 
> technically 
> > adding another layer of indirection in the picture.  Within 
> dom0, qemu-dm 
> > has direct access to the hardware.  Fortunately, the Xen 
> BE/FE model is 
> > quite good performance wise so there shouldn't be a 
> performance regression 
> > here.
> >
> >> but I'm little bit confused about the relationship between 
> stub domain 
> >> and guest domain. Is the stub domain part of guest domain? 
> Does each 
> >> guest domain have a stub domain which is created when the 
> guest domain is 
> >> created?
> >
> > A lot of this is still being worked out.  From a user 
> perspective, the 
> > idea would be that creating an HVM domain would be 
> identical to how it's 
> > done today.  What happens under the covers though remains 
> to be seen.
> >
> > Regards,
> >
> > Anthony Liguori
> >
> >> If the stub domain is part of guest domain, does porting 
> device model to 
> >> stub domain compromise the orginial design purpose of 
> isoloated devide 
> >> domain?
> >>
> >> Thanks,
> >>
> >> Liang
> >
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxxxxxxxx
> > http://lists.xensource.com/xen-devel
> > 
> 
> 
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> 
> 
> 



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