Re: [Xen-devel] extend shared_info stuct

[Kerti Csaba <csocskos@xxxxxxxxxxx>]

----------------------------------------
> Date: Mon, 30 Jul 2012 15:59:39 +0100
> From: JBeulich@xxxxxxxx
> To: csocskos@xxxxxxxxxxx
> CC: xen-devel@xxxxxxxxxxxxx
> Subject: Re: [Xen-devel] extend shared_info stuct
>
> >>> On 30.07.12 at 16:24, Kerti Csaba <csocskos@xxxxxxxxxxx> wrote:
> > In my small experiment, I would like to extend the shared_info stuct of the
> > hypervisor in the xen/include/public/xen.h with few variables. I already 
> > made
> > a try, but I failed. I like to do this, because I want to store/read public
> > values between the guests and the domain0.
> > I tried to add these fields to the end of the shared_info. I did “make” it
> > and install it. (I avoid the size checker of the shared_info).
>
> Avoiding the size checker is certainly a mistake - it's there for a
> reason.
>
> > As I know, the guest operation system should know this modification, so I
> > modified the guest op system at include/xen/interface/xen.h (ubuntu 11.04). 
> > I
> > was a bit surprised because the two interface (xen.h) was not the same, even
> > in the shared_info stuct there was some different (in the pvclock_wall wc
> > definition).
> >
> > The operation system of the domain0 should be changed as well ?? Just in
> > case I made the same modification. (ubuntu 12.04)
> >
> > I tried out the system with an already existing virtual machine to add it
> > with the xm create with the following variables:
> > modified xen + modified dom0 kernel + modified guest kernel => failed to 
> > boot
> > modified xen + original dom0 kernel + modified guest kernel => failed to 
> > boot
> > modified xen + original dom0 kernel + original guest kernel => failed to 
> > boot
>
> You fail to say what failed to boot - Dom0 or DomU.
>
> > original xen + original dom0 kernel + original guest kernel => successfully
> > boot
> >
> > So my question is that how can I add extra fields to the shared_info?
> > what do I need to modify in the guest kernel?
> > do I need any modification in dom0?
>
> Of course all modifications must be done uniformly to every
> component using the PV ABI. Nothing else should be required,
> provided you do the changes correctly (which includes not
> extending the shared info structure beyond a page in size).
>
> Perhaps the better approach for your purposes would be to
> have the domains actively register a separate shared data
> region with the hypervisor, similar to the extension of being
> able to register the per-vCPU info area to a location outside
> of the shared info page.
>
> Jan

Thank you Jan!

I'm looking up this per-vCPU info area!
Anyway, always the guest domain was which failed to boot.

Csaba                                     
_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel