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Re: [Qemu-devel] [PATCH] mttcg: Set jmp_env to handle exit from tb_gen_c
From: |
Alex Bennée |
Subject: |
Re: [Qemu-devel] [PATCH] mttcg: Set jmp_env to handle exit from tb_gen_code |
Date: |
Mon, 20 Feb 2017 16:16:13 +0000 |
User-agent: |
mu4e 0.9.19; emacs 25.2.4 |
Pranith Kumar <address@hidden> writes:
> tb_gen_code() can exit execution using cpu_exit_loop() when it cannot
> allocate new tb's. To handle this, we need to properly set the jmp_env
> pointer ahead of calling tb_gen_code().
>
> CC:Alex Bennée <address@hidden>
> CC: Richard Henderson <address@hidden>
> Signed-off-by: Pranith Kumar <address@hidden>
> ---
> cpu-exec.c | 23 +++++++++++------------
> 1 file changed, 11 insertions(+), 12 deletions(-)
>
> diff --git a/cpu-exec.c b/cpu-exec.c
> index 97d79612d9..4b70988b24 100644
> --- a/cpu-exec.c
> +++ b/cpu-exec.c
> @@ -236,23 +236,22 @@ static void cpu_exec_step(CPUState *cpu)
>
> cpu_get_tb_cpu_state(env, &pc, &cs_base, &flags);
> tb_lock();
> - tb = tb_gen_code(cpu, pc, cs_base, flags,
> - 1 | CF_NOCACHE | CF_IGNORE_ICOUNT);
> - tb->orig_tb = NULL;
> - tb_unlock();
> -
> - cc->cpu_exec_enter(cpu);
> -
It occurs to me we are also diverging in our locking pattern from
tb_find which takes mmap_lock first. This is a NOP for system emulation
but needed for user-emulation (for which we can do cpu_exec_step but not
cpu_exec_nocache).
> if (sigsetjmp(cpu->jmp_env, 0) == 0) {
> + tb = tb_gen_code(cpu, pc, cs_base, flags,
> + 1 | CF_NOCACHE | CF_IGNORE_ICOUNT);
> + tb->orig_tb = NULL;
> + tb_unlock();
> +
> + cc->cpu_exec_enter(cpu);
> /* execute the generated code */
> trace_exec_tb_nocache(tb, pc);
> cpu_tb_exec(cpu, tb);
> - }
> + cc->cpu_exec_exit(cpu);
>
> - cc->cpu_exec_exit(cpu);
> - tb_lock();
> - tb_phys_invalidate(tb, -1);
> - tb_free(tb);
> + tb_lock();
> + tb_phys_invalidate(tb, -1);
> + tb_free(tb);
> + }
> tb_unlock();
> }
--
Alex Bennée