[Xen-ia64-devel] [PATCH] get_pfn_list workaround

["Xu, Anthony" <anthony.xu@xxxxxxxxx>]

As we know, the mechanism for hypervisor to pass parameter through pointer
 is not complete. Hypervisor use copy_from/to_user functions to copy parameter
to hypervisor and copy result to user, if there is a tlb miss happening and 
hypervisor can't handled this. This hypercall fails, there is no mechanism to 
handle this failure, that may cause domain crash. Get_pfn_list hypercall copy
large data from hypervisor to user, it is easy to trigger this issue when 
creating VTI-domain.

If fails, Get_pfn_list returns the number of pfn entries, and this patch will 
Dummy access parameter memory block to cause this tlb mapping tracked by 
Hypervisor, then continue to do get_pfn_list.

It's a workaround before we design a new mechanism of passing parameter thr
pointer.

Signed-off-by: Anthony Xu <anthony.xu@xxxxxxxxx>
.
Thanks,
-Anthony

get_pfn_list.diff
Description: get_pfn_list.diff

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