[Bug 1861605] Re: LL/SC broken for MIPS after 7dd547e5ab6b31e7a0cfc182d3ad131dd55a948f

[Thomas Huth]

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

** Changed in: qemu
       Status: New => Fix Committed

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Title:
  LL/SC broken for MIPS after 7dd547e5ab6b31e7a0cfc182d3ad131dd55a948f

Status in QEMU:
  Fix Committed

Bug description:
  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.

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