Re: [Xen-devel] dom0 pvops crash

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

On 01/27/2010 11:18 AM, Ian Campbell wrote:
> > That's a thought.  It could be generally useful too; highpte should only
> > be used in extreme circumstances (to prevent ptes from filling most of
> > lowmem), not on every system with highmem.   IOW use a generic flag
> > rather than make it explicitly Xen-related, then we can set that flag.
> >      
> I think this is the most plausible idea. Need to think about what
> criteria would be used to set the flag on native, simply raw RAM size?
> i.e. you wouldn't use HIGHPTE on a 4G system, even if CONFIG_HIGHPTE is
> enabled, but where would the cut-off be?
>
> Rather than a flag I guess I'd make a pte_gfp variable which could be
> modified to suit.
>    
Well, you could try heuristicing it up, but I suspect a simpler approach 
is just a variable which is enabled by command line and/or config 
option.  HIGHPTE is an arch-independent concept, but the policy for 
defaulting it is arch-specific; on x86 it should almost always be off.
> > Or we could just put a big fat config dependency in.
> >      
> I'd imagine that seemingly random "depends !XEN" would be unpopular
> upstream.
>    
I was thinking the other way around; Xen depends on !HIGHPTE.  But a 
runtime switch would be just as good.
    J

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