Re: [Qemu-devel] [PATCH v2] cpu-exec: Do not invalidate original TB in cpu_exec_nocache()

[Sergey Fedorov <serge.fdrv@gmail.com>]

ping.

On 30.06.2015 12:35, Sergey Fedorov wrote:
> Instead of invalidating an original TB in cpu_exec_nocache()
> prematurely, just save a link to it in the temporary generated TB. If
> cpu_io_recompile() is raised subsequently from the temporary TB,
> invalidate the original one as well. That allows reusing the original TB
> each time cpu_exec_nocache() is called to handle expired instruction
> counter in icount mode.
>
> Signed-off-by: Sergey Fedorov <serge.fdrv@gmail.com>
> ---
>
> v2:
>  * take tcg_ctx.tb_ctx.tb_invalidated_flag into account
>
>  cpu-exec.c              | 8 ++------
>  include/exec/exec-all.h | 2 ++
>  translate-all.c         | 8 ++++++++
>  3 files changed, 12 insertions(+), 6 deletions(-)
>
> diff --git a/cpu-exec.c b/cpu-exec.c
> index 2ffeb6e..f3468e8 100644
> --- a/cpu-exec.c
> +++ b/cpu-exec.c
> @@ -231,19 +231,15 @@ static void cpu_exec_nocache(CPUArchState *env, int max_cycles,
>  {
>      CPUState *cpu = ENV_GET_CPU(env);
>      TranslationBlock *tb;
> -    target_ulong pc = orig_tb->pc;
> -    target_ulong cs_base = orig_tb->cs_base;
> -    uint64_t flags = orig_tb->flags;
>  
>      /* Should never happen.
>         We only end up here when an existing TB is too long.  */
>      if (max_cycles > CF_COUNT_MASK)
>          max_cycles = CF_COUNT_MASK;
>  
> -    /* tb_gen_code can flush our orig_tb, invalidate it now */
> -    tb_phys_invalidate(orig_tb, -1);
> -    tb = tb_gen_code(cpu, pc, cs_base, flags,
> +    tb = tb_gen_code(cpu, orig_tb->pc, orig_tb->cs_base, orig_tb->flags,
>                       max_cycles | CF_NOCACHE);
> +    tb->orig_tb = tcg_ctx.tb_ctx.tb_invalidated_flag ? NULL : orig_tb;
>      cpu->current_tb = tb;
>      /* execute the generated code */
>      trace_exec_tb_nocache(tb, tb->pc);
> diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
> index 2573e8c..2aab8c3 100644
> --- a/include/exec/exec-all.h
> +++ b/include/exec/exec-all.h
> @@ -155,6 +155,8 @@ struct TranslationBlock {
>      void *tc_ptr;    /* pointer to the translated code */
>      /* next matching tb for physical address. */
>      struct TranslationBlock *phys_hash_next;
> +    /* original tb when cflags has CF_NOCACHE */
> +    struct TranslationBlock *orig_tb;
>      /* first and second physical page containing code. The lower bit
>         of the pointer tells the index in page_next[] */
>      struct TranslationBlock *page_next[2];
> diff --git a/translate-all.c b/translate-all.c
> index b6b0e1c..5520f93 100644
> --- a/translate-all.c
> +++ b/translate-all.c
> @@ -1532,6 +1532,14 @@ void cpu_io_recompile(CPUState *cpu, uintptr_t retaddr)
>      cs_base = tb->cs_base;
>      flags = tb->flags;
>      tb_phys_invalidate(tb, -1);
> +    if (tb->cflags & CF_NOCACHE) {
> +        if (tb->orig_tb) {
> +            /* Invalidate original TB if this TB was generated in
> +             * cpu_exec_nocache() */
> +            tb_phys_invalidate(tb->orig_tb, -1);
> +        }
> +        tb_free(tb);
> +    }
>      /* FIXME: In theory this could raise an exception.  In practice
>         we have already translated the block once so it's probably ok.  */
>      tb_gen_code(cpu, pc, cs_base, flags, cflags);