On 28 Jul 2006, at 16:51, Ian Pratt wrote:

My only fear is that batched wrpt has some guest-visible effects. For example, the guest has to be able to cope with seeing page directory entries with the present bit cleared. Also, on SMP, it has to be able to cope with spurious page faults anywhere in its address space (e.g., faults on a unhooked page table which some other VCPU has rehooked by the time the Xen pagefault handler runs, hence the fault is bounced back to the guest even though there is no work to be done). If we turn off batched wrpt then guests will not be tested against it and we are likely to hit problems if we ever want to turn it back on again -- we'll find that some guests are not able to correctly handle the weird side effects.

On the other hand, perhaps we can find a neater more explicit alternative to batched wrpt in future.

-- Keir