Re: [PATCH v5 14/17] include/hw/core: Create struct CPUJumpCache

["Alex Bennée" <alex.bennee@linaro.org>]

Richard Henderson <richard.henderson@linaro.org> writes:

> Wrap the bare TranslationBlock pointer into a structure.
>
> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  include/hw/core/cpu.h     | 8 ++++++--
>  accel/tcg/cpu-exec.c      | 9 ++++++---
>  accel/tcg/cputlb.c        | 2 +-
>  accel/tcg/translate-all.c | 4 ++--
>  4 files changed, 15 insertions(+), 8 deletions(-)
>
> diff --git a/include/hw/core/cpu.h b/include/hw/core/cpu.h
> index 9e47184513..ee5b75dea0 100644
> --- a/include/hw/core/cpu.h
> +++ b/include/hw/core/cpu.h
> @@ -232,6 +232,10 @@ struct hvf_vcpu_state;
>  #define TB_JMP_CACHE_BITS 12
>  #define TB_JMP_CACHE_SIZE (1 << TB_JMP_CACHE_BITS)
>  
> +typedef struct {
> +    TranslationBlock *tb;
> +} CPUJumpCache;
> +

I don't quite follow whats going on here. I see we add vaddr pc in a
later patch but I don't quite see why a cache for looking up TBs gets a
sidechan value added later.

Is this because the vaddr will no longer match the tb->pc? Maybe a
comment on the structure is needed?

>  /* work queue */
>  
>  /* The union type allows passing of 64 bit target pointers on 32 bit
> @@ -361,7 +365,7 @@ struct CPUState {
>      IcountDecr *icount_decr_ptr;
>  
>      /* Accessed in parallel; all accesses must be atomic */
> -    TranslationBlock *tb_jmp_cache[TB_JMP_CACHE_SIZE];
> +    CPUJumpCache tb_jmp_cache[TB_JMP_CACHE_SIZE];
>  
>      struct GDBRegisterState *gdb_regs;
>      int gdb_num_regs;
> @@ -452,7 +456,7 @@ static inline void cpu_tb_jmp_cache_clear(CPUState *cpu)
>      unsigned int i;
>  
>      for (i = 0; i < TB_JMP_CACHE_SIZE; i++) {
> -        qatomic_set(&cpu->tb_jmp_cache[i], NULL);
> +        qatomic_set(&cpu->tb_jmp_cache[i].tb, NULL);
>      }
>  }
>  
> diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
> index dd58a144a8..c6283d5798 100644
> --- a/accel/tcg/cpu-exec.c
> +++ b/accel/tcg/cpu-exec.c
> @@ -252,7 +252,7 @@ static inline TranslationBlock *tb_lookup(CPUState *cpu, target_ulong pc,
>      tcg_debug_assert(!(cflags & CF_INVALID));
>  
>      hash = tb_jmp_cache_hash_func(pc);
> -    tb = qatomic_rcu_read(&cpu->tb_jmp_cache[hash]);
> +    tb = qatomic_rcu_read(&cpu->tb_jmp_cache[hash].tb);
>  
>      if (likely(tb &&
>                 tb->pc == pc &&
> @@ -266,7 +266,7 @@ static inline TranslationBlock *tb_lookup(CPUState *cpu, target_ulong pc,
>      if (tb == NULL) {
>          return NULL;
>      }
> -    qatomic_set(&cpu->tb_jmp_cache[hash], tb);
> +    qatomic_set(&cpu->tb_jmp_cache[hash].tb, tb);
>      return tb;
>  }
>  
> @@ -987,6 +987,8 @@ int cpu_exec(CPUState *cpu)
>  
>              tb = tb_lookup(cpu, pc, cs_base, flags, cflags);
>              if (tb == NULL) {
> +                uint32_t h;
> +
>                  mmap_lock();
>                  tb = tb_gen_code(cpu, pc, cs_base, flags, cflags);
>                  mmap_unlock();
> @@ -994,7 +996,8 @@ int cpu_exec(CPUState *cpu)
>                   * We add the TB in the virtual pc hash table
>                   * for the fast lookup
>                   */
> -                qatomic_set(&cpu->tb_jmp_cache[tb_jmp_cache_hash_func(pc)], tb);
> +                h = tb_jmp_cache_hash_func(pc);
> +                qatomic_set(&cpu->tb_jmp_cache[h].tb, tb);
>              }
>  
>  #ifndef CONFIG_USER_ONLY
> diff --git a/accel/tcg/cputlb.c b/accel/tcg/cputlb.c
> index f5e6ca2da2..fb8f3087f1 100644
> --- a/accel/tcg/cputlb.c
> +++ b/accel/tcg/cputlb.c
> @@ -103,7 +103,7 @@ static void tb_jmp_cache_clear_page(CPUState *cpu, target_ulong page_addr)
>      unsigned int i, i0 = tb_jmp_cache_hash_page(page_addr);
>  
>      for (i = 0; i < TB_JMP_PAGE_SIZE; i++) {
> -        qatomic_set(&cpu->tb_jmp_cache[i0 + i], NULL);
> +        qatomic_set(&cpu->tb_jmp_cache[i0 + i].tb, NULL);
>      }
>  }
>  
> diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
> index f429d33981..efa479ccf3 100644
> --- a/accel/tcg/translate-all.c
> +++ b/accel/tcg/translate-all.c
> @@ -1187,8 +1187,8 @@ static void do_tb_phys_invalidate(TranslationBlock *tb, bool rm_from_page_list)
>      /* remove the TB from the hash list */
>      h = tb_jmp_cache_hash_func(tb->pc);
>      CPU_FOREACH(cpu) {
> -        if (qatomic_read(&cpu->tb_jmp_cache[h]) == tb) {
> -            qatomic_set(&cpu->tb_jmp_cache[h], NULL);
> +        if (qatomic_read(&cpu->tb_jmp_cache[h].tb) == tb) {
> +            qatomic_set(&cpu->tb_jmp_cache[h].tb, NULL);
>          }
>      }


-- 
Alex Bennée