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Re: [PATCH v5 07/18] target/riscv: setup everything so that riscv128-sof

From: Frédéric Pétrot
Subject: Re: [PATCH v5 07/18] target/riscv: setup everything so that riscv128-softmmu compiles
Date: Thu, 25 Nov 2021 15:44:30 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.3.0

On 25/11/2021 12:47, Alistair Francis wrote:
On Wed, Nov 24, 2021 at 5:33 PM Philippe Mathieu-Daudé <f4bug@amsat.org> wrote:

Hi Frédéric,

On 11/24/21 07:55, Frédéric Pétrot wrote:
On 24/11/2021 07:12, Alistair Francis wrote:
On Sat, Nov 13, 2021 at 1:16 AM Frédéric Pétrot
<frederic.petrot@univ-grenoble-alpes.fr> wrote:

This patch is kind of a mess because several files have to be slightly
modified to allow for a new target. In the current status, we have done
our best to have RV64 and RV128 under the same RV64 umbrella, but there
is still work to do to have a single executable for both.
In particular, we have no atomic accesses for aligned 128-bit addresses.

Once this patch applied, adding risc128-sofmmu to --target-list produces
a (no so useful yet) executable.

I can't remember if we discussed this before, but do we need the
riscv128-sofmmu executable? Can we instead just use a riscv64-sofmmu

   Hello Alistair,
   Richard was also advocating for a single executable, but pointed out that
   we need to disable mttcg because there is a need for specific tcg
support for
   128-bit aligned atomics.
   Given my understanding of that part of QEMU, I choose the easy way to
   it once and for all at compile time until we have that.

In rv128_base_cpu_init():

   if (qemu_tcg_mttcg_enabled) {
       /* Missing 128-bit aligned atomics */
       error_report("128-bit RISC-V currently does not work"
                    " with Multi Threaded TCG. Please use:"
                    " -accel tcg,thread=single");

That seems like a good option! I think we could add this to the CPU
realise function.

The problem with a riscv128-sofmmu executable is that it's hard to get
rid of in the future. We are very slowly moving towards a single
executable and adding a new one means we are stuck with it for a


  Ooups, I replied yesterday to Philippe that I would work that out, but I
  missed the reply all button, sorry.




| Frédéric Pétrot, Pr. Grenoble INP-Ensimag/TIMA,   Ensimag deputy director |
| Mob/Pho: +33 6 74 57 99 65/+33 4 76 57 48 70      Ad augusta  per angusta |
| http://tima.univ-grenoble-alpes.fr frederic.petrot@univ-grenoble-alpes.fr |

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