[Xen-devel] RE: [patch 14/21] Xen-paravirt: Add XEN config options and disableunsupported config options.

["Christian Limpach" <Christian.Limpach@xxxxxxxxxxxxx>]

Jeremy Fitzhardinge wrote:
> Andrew Morton wrote:
> > On Thu, 15 Feb 2007 22:14:45 -0800 Dan Hecht 
> <dhecht@xxxxxxxxxx> wrote:
> >
> >   
> >>>  config PREEMPT
> >>>   bool "Preemptible Kernel (Low-Latency Desktop)"
> >>> + depends on !XEN
> >>>   help
> >>>     This option reduces the latency of the kernel by making
> >>>     all kernel code (that is not executing in a critical section)
> >>>
> >>>       
> >
> > Oh, so that's why it doesn't break when CONFIG_PREEMPT=y.  
> In which case
> > that preempt_disable() I spotted is wrong-and-unneeded.
> >
> > Why doesn't Xen work with preemption??
> >   
> 
> I've forgotten the details.  Ian?  Keir?  Steven?  Maybe it 
> can be done.

With CONFIG_PREEMPT, we can have preempted threads reference machine
addresses across save/restore.  After restore, these machine addresses
will be incorrect.

    Christian

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