RE: [Xen-devel] Re: user/hypervisor address space solution

["Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>]

> But while we're on the subject, I recall hearing that IA64 
> has an issue
> with TLB faults when accessing domain virtual addresses. Could you
> elaborate on that? I guess you're using a software-controlled TLB, and
> when a fault occurs you need to call up to Linux to handle it?

This is a theoretical problem that is believed to be a possible
issue. Yes, if a user access is made that is not in the TLB, a trap
occurs and it is at least conceivable that Xen will be unable
to resolve it and the trap would be reflected to the guest.
This would necessitate a restart of the hypercall and, if
a hypercall requires two user accesses to different pages
(perhaps maliciously), it seems possible that thrashing could occur.

This deserves some detailed study but there have been much
bigger fish to fry :-)

Dan

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