[Xen-devel] [PATCH] xencomm, xenmem and hypercall continuation

[Isaku Yamahata <yamahata@xxxxxxxxxxxxx>]

fix xenmem hypercall for non-trivial xencomm arch(i.e. ia64, and powerpc)
On ia64 and powerpc, guest_handle_add_offset() effect persists over
hypercall continuation because its consumed offset is recorced in
guest domains memory space.
On the other hand, x86 guest_handle_add_offset() effect is volatile
over hypercall continuation.
So xenmem hypercall(more specifically increase_reservation,
decrease_reservaton, populate_memory and exchange) is broken on
ia64 and powerpc.
#ifdef/ifndef CONFIG_X86 is used to solve this issue without breaking
the existing ABI. #ifdef is ugly, but it would be difficult to solve
this issue without #ifdef and to preserve the existing ABI simaltaneously.

I checked other users of both guest_handle_add_offset() and hypercall
continuation. Fortunately other users records restart points
by hypercall argument so that this isn't an issue.


-- 
yamahata

Attachment: 12315_f3e97d467b6f_xencomm_and_xenmem_hypercall.patch
Description: Text document

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