Re: [Qemu-devel] [RFC v3 PATCH 4/5] mttcg: Implement implicit ordering semantics

[Richard Henderson]

On 08/28/2017 11:33 PM, Pranith Kumar wrote:
> Currently, we cannot use mttcg for running strong memory model guests
> on weak memory model hosts due to missing ordering semantics.
> 
> We implicitly generate fence instructions for stronger guests if an
> ordering mismatch is detected. We generate fences only for the orders
> for which fence instructions are necessary, for example a fence is not
> necessary between a store and a subsequent load on x86 since its
> absence in the guest binary tells that ordering need not be
> ensured. Also note that if we find multiple subsequent fence
> instructions in the generated IR, we combine them in the TCG
> optimization pass.
> 
> This patch allows us to boot an x86 guest on ARM64 hosts using mttcg.
> 
> Signed-off-by: Pranith Kumar <address@hidden>
> ---
>  tcg/tcg-op.c | 16 ++++++++++++++++
>  1 file changed, 16 insertions(+)

Reviewed-by: Richard Henderson <address@hidden>


r~