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Re: [Qemu-devel] [PATCH RFC v1 1/3] target/ppc: Emulate LL/SC using cmpx
From: |
Nikunj A Dadhania |
Subject: |
Re: [Qemu-devel] [PATCH RFC v1 1/3] target/ppc: Emulate LL/SC using cmpxchg helpers |
Date: |
Fri, 07 Apr 2017 10:44:03 +0530 |
User-agent: |
Notmuch/0.23.5 (https://notmuchmail.org) Emacs/25.1.1 (x86_64-redhat-linux-gnu) |
Richard Henderson <address@hidden> writes:
> On 04/06/2017 03:22 AM, Nikunj A Dadhania wrote:
>> tcg_gen_trunc_tl_i32(cpu_crf[0], cpu_so);
>> l1 = gen_new_label();
>> tcg_gen_brcond_tl(TCG_COND_NE, EA, cpu_reserve, l1);
>> - tcg_gen_ori_i32(cpu_crf[0], cpu_crf[0], CRF_EQ);
>> - tcg_gen_qemu_st_tl(cpu_gpr[reg], EA, ctx->mem_idx, memop);
>> +
>> + t0 = tcg_temp_new();
>> + tcg_gen_atomic_cmpxchg_tl(t0, EA, cpu_reserve_val, cpu_gpr[reg],
>> + ctx->mem_idx, DEF_MEMOP(memop));
>
> Actually, I noticed another, existing, problem.
>
> This code changes CRF[0] before the user memory write, which might fault.
> This
> needs to delay any changes to the architecture visible state until after any
> exception may be triggered.
Sure, here you are mentioning cpu_so being moved to CRF.
Regards
Nikunj