LL/SC broken for MIPS after 7dd547e5ab6b31e7a0cfc182d3ad131dd55a948f

[Alexander Richardson]

In that commit the env->llval value is loaded as an unsigned value (instead of sign-extended as before and therefore the CMPXCHG in gen_st_cond() in translate.c fails.

I have committed a fix for this issue as https://github.com/qemu/qemu/commit/6ff8dec97f1a105d0da96c67ee24c75e437df162

An alternative solution would be to change the cmpxchg line to perform a non-sign-extended compare, i.e. replace
    tcg_gen_atomic_cmpxchg_tl(t0, cpu_lladdr, cpu_llval, val,
                              eva ? MIPS_HFLAG_UM : ctx->mem_idx, tcg_mo);
with
    tcg_gen_atomic_cmpxchg_tl(t0, cpu_lladdr, cpu_llval, val,
                              eva ? MIPS_HFLAG_UM : ctx->mem_idx, tcg_mo & ~MO_SIGN);

However, that change does not fix the fact that the result of ll is no longer sign-extended, therefore I think adding a cast in the helpers is better.

I cannot send this patch to the QEMU mailing list as I am not able to setup git-send-email.
Feel free to apply this commit or the alternative solution.

[Alexander Richardson (arichardson)]

The fix I linked is incorrect, the correct URL is https://github.com/CTSRD-CHERI/qemu/commit/a833317eeb0387dcfa7615a78e74f8b48990b8bc

[Alexander Richardson (arichardson)]

New patch: https://github.com/qemu/qemu/commit/6ff8dec97f1a105d0da96c67ee24c75e437df162

[Thomas Huth (th-huth)]

Patch has been merged here:
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=ec860426dfbebe0c