Re: [Qemu-devel] [PATCH 12/15] s390x: reduce TARGET_PHYS_ADDR_SPACE_BITS to 62

[Paolo Bonzini]

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 <address@hidden>
> > Signed-off-by: Paolo Bonzini <address@hidden>
> 
> 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.

Paolo