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

[Alexander Richardson]

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

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https://bugs.launchpad.net/bugs/1861605

Title:
  LL/SC broken for MIPS after 7dd547e5ab6b31e7a0cfc182d3ad131dd55a948f

Status in QEMU:
  New

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/CTSRD-
  CHERI/qemu/commit/a18d80c629989d002794f558968e1561edaf3dfd

  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, addr, cpu_llval, val,
                                eva ? MIPS_HFLAG_UM : ctx->mem_idx, tcg_mo); 
  with
      tcg_gen_atomic_cmpxchg_tl(t0, addr, cpu_llval, val,
                                eva ? MIPS_HFLAG_UM : ctx->mem_idx, tcg_mo & 
~MO_SIGN); 

  
  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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