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RE: [Xen-devel] [PATCH 1/9] Add cpu idle pwr mgmt to xen

>>> "Tian, Kevin" <kevin.tian@xxxxxxxxx> 30.04.08 11:12 >>>
>One thing kicking me just now is, whether Linux address check
>style can be used here by temporarily increasing address limit
>in compat logic to bypass relative check in common code? I
>didn't see obvious benefit to reserve a guest virtual addr range
>and let each component to manage internal allocation themselves.
>Linux style seems simpler and compat logic can just use xmalloc
>to create native copy to reduce xlat complexity.

I intentionally did not go that route when I first wrote these translation
routines. For one, you wouldn't be able to partly copy things (as I
suggested as an improvement here), since the validity checks would
apply to all or nothing during an individual hypercall (and a bad 64-bit
field representing a pointer might then slip through). Secondly, the
static pre-allocation used currently also avoids spurious failures of
hypercalls (there may be deterministic failures if the combined set
of indirect hypercall arguments exceeds the pre-allocation size.


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