Re: [Xen-devel] [PATCH for-4.5 v6 12/17] xen/arm: Implement domain_get_maximum_gpfn

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Tue, 2014-09-16 at 10:02 +0200, Tamas K Lengyel wrote:
> Certainly. The reason we use this in xenaccess is to avoid the user
> attempting to set page permissions on pages which don't exist for the
> domain. For example, if the user attempts to set page permissions from
> gpfn 0 -> (~0-1), it will waste a lot of the hypervisors time. It
> won't break anything as non-existent pages are skipped automatically,
> and now with the preemption in place it can't DoS the system, but it's
> still a reasonable sanity check to perform. It's not a comprehensive
> enforcement of 'don't try to set permission on non-existent pages' as
> ARM has holes in the memory layout and doesn't start from 0, but this
> check at least works for both x86 and ARM. 

OK. Please can you include this in the commit message.



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