Re: [PATCH 2/3] accel/tcg: Fix overwrite problems of tcg_cflags

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 1/4/23 06:51, Richard Henderson wrote:
> From: Weiwei Li <liweiwei@iscas.ac.cn>
> 
> CPUs often set CF_PCREL in tcg_cflags before qemu_init_vcpu(), in which
> tcg_cflags will be overwrited by tcg_cpu_init_cflags().

The description makes sense, but I couldn't reproduce using:

-- >8 --
diff --git a/accel/tcg/tcg-accel-ops.c b/accel/tcg/tcg-accel-ops.c
index af35e0d092..23ebf7de21 100644
--- a/accel/tcg/tcg-accel-ops.c
+++ b/accel/tcg/tcg-accel-ops.c
@@ -59,6 +59,7 @@ void tcg_cpu_init_cflags(CPUState *cpu, bool parallel)

      cflags |= parallel ? CF_PARALLEL : 0;
      cflags |= icount_enabled() ? CF_USE_ICOUNT : 0;
+    tcg_debug_assert(!cpu->tcg_cflags);
      cpu->tcg_cflags = cflags;
  }
---

Li and Junqiang, what is your use case?

> Fixes: 4be790263ffc ("accel/tcg: Replace `TARGET_TB_PCREL` with `CF_PCREL`")
> Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
> Signed-off-by: Weiwei Li <liweiwei@iscas.ac.cn>
> Signed-off-by: Junqiang Wang <wangjunqiang@iscas.ac.cn>
> Message-Id: <20230331150609.114401-6-liweiwei@iscas.ac.cn>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   accel/tcg/tcg-accel-ops.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/accel/tcg/tcg-accel-ops.c b/accel/tcg/tcg-accel-ops.c
> index af35e0d092..58c8e64096 100644
> --- a/accel/tcg/tcg-accel-ops.c
> +++ b/accel/tcg/tcg-accel-ops.c
> @@ -59,7 +59,7 @@ void tcg_cpu_init_cflags(CPUState *cpu, bool parallel)
>   
>       cflags |= parallel ? CF_PARALLEL : 0;
>       cflags |= icount_enabled() ? CF_USE_ICOUNT : 0;
> -    cpu->tcg_cflags = cflags;
> +    cpu->tcg_cflags |= cflags;

This could be acceptable as a release kludge, but semantically
tcg_cpu_init_cflags() is meant to *initialize* all flags, not
set few of them. Either we aren't calling it from the proper place,
or we need to rename it.

>   }
>   
>   void tcg_cpus_destroy(CPUState *cpu)