Re: [PATCH v3 00/57] tcg: Improve atomicity support

[Peter Maydell]

On Tue, 25 Apr 2023 at 20:32, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> v1: 
> https://lore.kernel.org/qemu-devel/20221118094754.242910-1-richard.henderson@linaro.org/
> v2: 
> https://lore.kernel.org/qemu-devel/20230216025739.1211680-1-richard.henderson@linaro.org/
>
> Based-on: 20230424054105.1579315-1-richard.henderson@linaro.org
> ("[PATCH v3 00/57] tcg: Simplify calls to load/store helpers")
>
> The main objective here is to support Arm FEAT_LSE2, which says that any
> single memory access that does not cross a 16-byte boundary is atomic.
> This is the MO_ATOM_WITHIN16 control.
>
> While I'm touching all of this, a secondary objective is to handle the
> atomicity of the IBM machines.  Both Power and s390x treat misaligned
> accesses as atomic on the lsb of the pointer.  For instance, an 8-byte
> access at ptr % 8 == 4 will appear as two atomic 4-byte accesses, and
> ptr % 4 == 2 will appear as four 3-byte accesses.

I hope you mean "four 2-byte accesses", although I'm never
quite sure how odd s390x can get :-)

-- PMM