linux-kernel - Re: [PATCH RFC 0/3] Add guest cpu

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Message-ID: <1346102820.8623.32.camel@lambeau>
Date:	Mon, 27 Aug 2012 16:27:00 -0500
From:	Michael Wolf <mjw@...ux.vnet.ibm.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
	peterz@...radead.org, mtosatti@...hat.com, glommer@...allels.com,
	mingo@...hat.com
Subject: Re: [PATCH RFC 0/3] Add guest cpu_entitlement reporting

On Mon, 2012-08-27 at 13:31 -0700, Avi Kivity wrote:
> On 08/27/2012 01:23 PM, Michael Wolf wrote:
> > > 
> > > How would a guest know what its entitlement is?
> > > 
> > > 
> >
> > Currently the Admin/management tool setting up the guests will put it on
> > the qemu commandline.  From this it is passed via an ioctl to the host.
> > The guest will get the value from the host via a hypercall.
> >
> > In the future the host could try and do some of it automatically in some
> > cases. 
> 
> Seems to me it's a meaningless value for the guest.  Suppose it is
> migrated to a host that is more powerful, and as a result its relative
> entitlement is reduced.  The value needs to be adjusted.

This is why I chose to manage the value from the sysctl interface rather
than just have it stored as a value in /proc.  Whatever tool was used to
migrate the vm could hopefully adjust the sysctl value on the guest.
> 
> This is best taken care of from the host side.

Not sure what you are getting at here.  If you are running in a cloud
environment, you purchase a VM with the understanding that you are
getting certain resources.  As this type of user I don't believe you
have any access to the host to see this type of information.  So the
user still wouldnt have a way to confirm that they are receiving what
they should be in the way of processor resources.

Would you please elaborate a little more on this?
> 



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