Re: [PATCH 23/25] [PATCH] paravirt hooks for arch initialization

[Glauber de Oliveira Costa]

Jeremy Fitzhardinge escreveu:
> Glauber de Oliveira Costa wrote:
> > On 8/9/07, Alan Cox <alan@xxxxxxxxxxxxxxxxxxx> wrote:
> >   
> > > > What's the EBDA actually used for?  The only place which seems to use
> > > > ebda_addr is in the e820 code to avoid that area as RAM.
> > > >       
> > > It belongs to the firmware.
> > >     
> > Wouldn't it be better, then, to just skip this step unconditionally if
> > we are running a paravirtualized guest? What do we from doing it?
> >   
>
> It's better to make discover_ebda() quietly cope with a missing ebda for
> whatever reason.  We could add an explicit interface to paravirt_ops to
> handle this one little corner, but it isn't very important, not very
> general and really its just clutter.  Its much better to have things
> cope with being virtualized quietly on their own rather than hit them
> all with the pv_ops hammer.   pv_ops is really for things where the
> hypervisor-specific code really has to get actively involved.
I think the idea you gave me earlier of using probe_kernel_address could
work. Xen/lguest/put_yours_here that won't use an ebda would then have 
to unmap the page, to make sure a read would fault.


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