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Re: [Qemu-devel] MTTCG memory ordering
From: |
Pranith Kumar |
Subject: |
Re: [Qemu-devel] MTTCG memory ordering |
Date: |
Wed, 12 Oct 2016 11:30:11 -0400 |
Hi Stefan,
Stefan Hajnoczi writes:
> Hi Pranith,
> I was curious about the status of your MTTCG GSoC work:
>
> I saw your fence series which implements the noop memory barrier/fence
> instructions on various architectures, but I wasn't sure if that also
> covers the case where a strong target is emulated on a weak host.
>
No, this work is still pending. The current implementation only supports weak
on strong (the simplest case) by emitting barriers explicitly.
> Did you make TCG automatically emit barriers so stronger targets (x86)
> run correctly on weaker targets (ARM)?
We did consider doing this by emitting barriers implicitly for each memory
instruction of a strong target but decided that it would be too costly. There
is, AFAIK, no trivial solution to avoiding this overhead as of now.
I will start working on this next step soon, once I finish the tcg test setup.
Thanks,
--
Pranith