Re: [Qemu-devel] [RFC for 2.8 0/3] Drop support for 64 bit guests on 32 bit hosts

["Alex Bennée" <alex.bennee@linaro.org>]

Alex Bennée <alex.bennee@linaro.org> writes:

> Hi,
>
> I'm proposing for the 2.8 cycle we officially drop supporting 64 bit
> guests on 32 bit hosts. For most of the KVM targets it doesn't make
> any sense anyway and for TCG it makes things harder (e.g. supporting
> 64 bit atomics on a 32 bit platform). I'm not actually convinced
> things actually work if built or that anyone relies on these
> combinations. Consider these patches a way of flushing any such users
> out ;-)

So the other use case which got mentioned to me today was developers who
want to test 64 bit system emulation on 32 bit ARM chromebooks. So
together with Xen's use case it seems this isn't going to fly for this
cycle.

I suspect for working atomics in MTTCG though we'll need to stick to
single threaded mode on these combinations.

>
> Alex Bennée (3):
>   configure: check CPU width and disable larger guests
>   configure: filter 64 bit machines on 32 bit builds
>   cpu-defs.h: add compile check for HOST vs TARGET LONG_BITS
>
>  configure               | 50 +++++++++++++++++++++++++++++++++++++++++++++++--
>  include/exec/cpu-defs.h |  9 +++++++++
>  2 files changed, 57 insertions(+), 2 deletions(-)


--
Alex Bennée