Re: [Xen-devel] Baffled by multipage_allocation_permitted()

[Keir Fraser <keir.fraser@xxxxxxxxxxxxx>]

On 16/06/2009 14:10, "Dave McCracken" <dcm@xxxxxxxx> wrote:

> Thanks for the change.  That resolves my problem.
> 
> Out of curiosity, why is it necessary to restrict the size of multipage
> allocations at all?  I'd think the memory size limits would adequately protect
> against any guest going wild with it.  What harm could come from, for example,
> a guest asking for a 16M contiguous page?  I don't know of any current need
> for such a thing.  I'm just wondering why we restrict it.

Such regions could be a precious resource when driving some hardware devices
which communicate via large contiguous memory areas. As I said, we haven't
thought about it too hard, so it may indeed be sensible to relax this
further in future.

 -- Keir



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