Il 26/05/2013 23:08, Christian Borntraeger ha scritto: > On 26/05/13 21:07, Paolo Bonzini wrote: >> Il 26/05/2013 16:14, Andreas Färber ha scritto: >>>> With the next patch, the memory API will complain if the >>>> TARGET_PHYS_ADDR_SPACE_BITS gets dangerously close to an >>>> overflow. s390x can handle up to 64 bit of physical address >>>> space from its page tables, but we never use that much. Just >>>> decrease the value. >>>> >>>> Cc: Alexander Graf <ag...@suse.de> >>>> Signed-off-by: Paolo Bonzini <pbonz...@redhat.com> >>> >>> Didn't Avi introduce 128-bit arithmetic into QEMU to avoid 64-bit values >>> overflowing? Why are you limiting Memory API to 62-bit now? >> >> The next patch makes a difference between artificial memory regions >> (containers and aliases) which can have arbitrary placement and width, >> and the final view of the address space which cannot have a full 64-bit >> size. >> >> 63 bits probably would work, but I preferred to be safe since 62 is the >> largest used by other targets. >> >> It should be fixable, but if it is not a problem I wouldn't worry much >> about it. > > I would prefer to allow 64bit of address space. Memory on s390x can be > discontiguous. It is currently not used under KVM and it might not make > a lot of sense, but the current KVM code would allow a guest that has a > layout of lets say 0...1GB + 16EB-1GB...16EB. > > Furthermore, I know of some (prototype only) hw memory devices that actually > populated the upper memory addresses. If such a thing becomes reality in the > future we cannot provide virtualization of those.
Ok, I'll drop this patch and the next one from the pull request. Paolo