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[Bug 1861605] Re: LL/SC broken for MIPS after 7dd547e5ab6b31e7a0cfc182d3
From: |
Thomas Huth |
Subject: |
[Bug 1861605] Re: LL/SC broken for MIPS after 7dd547e5ab6b31e7a0cfc182d3ad131dd55a948f |
Date: |
Wed, 05 Feb 2020 17:15:14 -0000 |
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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https://bugs.launchpad.net/bugs/1861605
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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