Re: [Qemu-devel] [PATCH 3/4] exec: [tcg] Switch physical TB cache based on vCPU tracing state

[Lluís Vilanova]

Lluís Vilanova writes:

> Uses the per-vCPU event state in CPUState->trace_dstate (a bitmap) as an
> index to a physical TB cache that will contain code specific to the set
> of dynamically enabled events.

> Two vCPUs tracing different events will execute code from different
> physical TB caches. Two vCPUs tracing the same events will execute code
> from the same physical TB cache.

> This is used on the next patch to optimize TCG code related to event
> tracing.

> Signed-off-by: Lluís Vilanova <address@hidden>
> ---
>  cpu-exec.c             |    6 ++++++
>  trace/control-target.c |    2 ++
>  trace/control.h        |    3 +++
>  translate-all.c        |   23 +++++++++++++++++++++++
>  translate-all.h        |   26 ++++++++++++++++++++++++++
>  5 files changed, 60 insertions(+)

[...]
> diff --git a/translate-all.c b/translate-all.c
> index c864eee..c306cf4 100644
> --- a/translate-all.c
> +++ b/translate-all.c
> @@ -1166,6 +1166,29 @@ static void tb_link_page(TranslationBlock *tb, 
> tb_page_addr_t phys_pc,
>  #endif
>  }
 
> +void cpu_tb_cache_set_request(CPUState *cpu)
> +{
> +    /*
> +     * Request is taken from cpu->trace_dstate and lazily applied into
> +     * cpu->tb_cache_idx at cpu_tb_cache_set_apply().
> +     */
> +    /* NOTE: Checked by all TBs in gen_tb_start(). */
> +    cpu->tcg_exit_req = true;
> +}
> +
> +bool cpu_tb_cache_set_requested(CPUState *cpu)
> +{
> +    return !bitmap_equal(cpu->trace_dstate, cpu->tb_cache_idx,
> +                         TRACE_VCPU_EVENT_COUNT);
> +}
> +
> +void cpu_tb_cache_set_apply(CPUState *cpu)
> +{
> +    bitmap_copy(cpu->tb_cache_idx, cpu->tb_cache_idx,
> +                TRACE_VCPU_EVENT_COUNT);

I forgot to update the patch before sending. This one should be:

    bitmap_copy(cpu->tb_cache_idx, cpu->trace_dstate,
                TRACE_VCPU_EVENT_COUNT);


I'll wait for other reviews before sending v2 with this fixed.




> +    tb_flush_jmp_cache_all(cpu);
> +}
> +
>  /* Called with mmap_lock held for user mode emulation.  */
>  TranslationBlock *tb_gen_code(CPUState *cpu,
>                                target_ulong pc, target_ulong cs_base,
[...]


Cheers,
  Lluis