Re: [PATCH v2 01/14] plugins: implement inline operation relative to cpu_index

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

Pierrick Bouvier <pierrick.bouvier@linaro.org> writes:

> Instead of working on a fixed memory location, allow to address it based
> on cpu_index, an element size and a given offset.
> Result address: ptr + offset + cpu_index * element_size.
>
> With this, we can target a member in a struct array from a base pointer.
>
> Current semantic is not modified, thus inline operation still targets
> always the same memory location.
>
> Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
> ---
>  accel/tcg/plugin-gen.c | 67 +++++++++++++++++++++++++++++++++++-------
>  include/qemu/plugin.h  |  3 ++
>  plugins/api.c          |  7 +++--
>  plugins/core.c         | 18 +++++++++---
>  plugins/plugin.h       |  6 ++--
>  5 files changed, 81 insertions(+), 20 deletions(-)
>
> diff --git a/accel/tcg/plugin-gen.c b/accel/tcg/plugin-gen.c
> index b37ce7683e6..1a2375d7779 100644
> --- a/accel/tcg/plugin-gen.c
> +++ b/accel/tcg/plugin-gen.c
> @@ -132,16 +132,28 @@ static void gen_empty_udata_cb_no_rwg(void)
>   */
>  static void gen_empty_inline_cb(void)
>  {
> +    TCGv_i32 cpu_index = tcg_temp_ebb_new_i32();
> +    TCGv_ptr cpu_index_as_ptr = tcg_temp_ebb_new_ptr();
>      TCGv_i64 val = tcg_temp_ebb_new_i64();
>      TCGv_ptr ptr = tcg_temp_ebb_new_ptr();
>  
> +    tcg_gen_ld_i32(cpu_index, tcg_env,
> +                   -offsetof(ArchCPU, env) + offsetof(CPUState, cpu_index));
> +    /* pass an immediate != 0 so that it doesn't get optimized away */
> +    tcg_gen_muli_i32(cpu_index, cpu_index, 0xdeadbeef);
> +    tcg_gen_ext_i32_ptr(cpu_index_as_ptr, cpu_index);
> +
>      tcg_gen_movi_ptr(ptr, 0);
> +    tcg_gen_add_ptr(ptr, ptr, cpu_index_as_ptr);
>      tcg_gen_ld_i64(val, ptr, 0);
>      /* pass an immediate != 0 so that it doesn't get optimized away */
>      tcg_gen_addi_i64(val, val, 0xdeadface);
> +
>      tcg_gen_st_i64(val, ptr, 0);
>      tcg_temp_free_ptr(ptr);
>      tcg_temp_free_i64(val);
> +    tcg_temp_free_ptr(cpu_index_as_ptr);
> +    tcg_temp_free_i32(cpu_index);
>  }
>  
<snip>
>      if (UINTPTR_MAX == UINT32_MAX) {
> @@ -395,18 +439,19 @@ static TCGOp *append_inline_cb(const struct qemu_plugin_dyn_cb *cb,
>                                 TCGOp *begin_op, TCGOp *op,
>                                 int *unused)
>  {
> -    /* const_ptr */
> -    op = copy_const_ptr(&begin_op, op, cb->userp);
> -
> -    /* ld_i64 */
> +    char *ptr = cb->userp;
> +    if (!cb->inline_direct_ptr) {
> +        /* dereference userp once to get access to memory location */
> +        ptr = *(char **)cb->userp;
> +    }

I'm confused here, probably because inline_direct_ptr gets removed later
on?

> +    op = copy_ld_i32(&begin_op, op);
> +    op = copy_mul_i32(&begin_op, op, cb->inline_element_size);
> +    op = copy_ext_i32_ptr(&begin_op, op);
> +    op = copy_const_ptr(&begin_op, op, ptr + cb->inline_offset);
> +    op = copy_add_ptr(&begin_op, op);
>      op = copy_ld_i64(&begin_op, op);
> -
> -    /* add_i64 */
>      op = copy_add_i64(&begin_op, op, cb->inline_insn.imm);
> -
> -    /* st_i64 */
>      op = copy_st_i64(&begin_op, op);
> -
>      return op;
>  }
>  
> diff --git a/include/qemu/plugin.h b/include/qemu/plugin.h
> index b0c5ac68293..9346249145d 100644
> --- a/include/qemu/plugin.h
> +++ b/include/qemu/plugin.h
> @@ -86,6 +86,9 @@ enum plugin_dyn_cb_subtype {
>  struct qemu_plugin_dyn_cb {
>      union qemu_plugin_cb_sig f;
>      void *userp;
> +    size_t inline_offset;
> +    size_t inline_element_size;
> +    bool inline_direct_ptr;

Ahh here it is.

(I seem to recall there is a setting for git to order headers first that
helps with this).

We could do with some documentation here. I can guess the offset and
element size values but what inline_direct_ptr means is not clear.

>      enum plugin_dyn_cb_subtype type;
>      /* @rw applies to mem callbacks only (both regular and inline) */
>      enum qemu_plugin_mem_rw rw;
> diff --git a/plugins/api.c b/plugins/api.c
> index 8d5cca53295..e777eb4e9fc 100644
> --- a/plugins/api.c
> +++ b/plugins/api.c
> @@ -106,7 +106,8 @@ void qemu_plugin_register_vcpu_tb_exec_inline(struct qemu_plugin_tb *tb,
>                                                void *ptr, uint64_t imm)
>  {
>      if (!tb->mem_only) {
> -        plugin_register_inline_op(&tb->cbs[PLUGIN_CB_INLINE], 0, op, ptr, imm);
> +        plugin_register_inline_op(&tb->cbs[PLUGIN_CB_INLINE],
> +                                  0, op, ptr, 0, sizeof(uint64_t), true, imm);
>      }
>  }
>  
> @@ -131,7 +132,7 @@ void qemu_plugin_register_vcpu_insn_exec_inline(struct qemu_plugin_insn *insn,
>  {
>      if (!insn->mem_only) {
>          plugin_register_inline_op(&insn->cbs[PLUGIN_CB_INSN][PLUGIN_CB_INLINE],
> -                                  0, op, ptr, imm);
> +                                  0, op, ptr, 0, sizeof(uint64_t), true, imm);
>      }
>  }
>  
> @@ -156,7 +157,7 @@ void qemu_plugin_register_vcpu_mem_inline(struct qemu_plugin_insn *insn,
>                                            uint64_t imm)
>  {
>      plugin_register_inline_op(&insn->cbs[PLUGIN_CB_MEM][PLUGIN_CB_INLINE],
> -                              rw, op, ptr, imm);
> +                              rw, op, ptr, 0, sizeof(uint64_t), true, imm);
>  }
>  
>  void qemu_plugin_register_vcpu_tb_trans_cb(qemu_plugin_id_t id,
> diff --git a/plugins/core.c b/plugins/core.c
> index 49588285dd0..e07b9cdf229 100644
> --- a/plugins/core.c
> +++ b/plugins/core.c
> @@ -280,13 +280,18 @@ static struct qemu_plugin_dyn_cb *plugin_get_dyn_cb(GArray **arr)
>  
>  void plugin_register_inline_op(GArray **arr,
>                                 enum qemu_plugin_mem_rw rw,
> -                               enum qemu_plugin_op op, void *ptr,
> +                               enum qemu_plugin_op op,
> +                               void *ptr, size_t offset, size_t element_size,
> +                               bool direct_ptr,
>                                 uint64_t imm)
>  {
>      struct qemu_plugin_dyn_cb *dyn_cb;
>  
>      dyn_cb = plugin_get_dyn_cb(arr);
>      dyn_cb->userp = ptr;
> +    dyn_cb->inline_element_size = element_size;
> +    dyn_cb->inline_offset = offset;
> +    dyn_cb->inline_direct_ptr = direct_ptr;
>      dyn_cb->type = PLUGIN_CB_INLINE;
>      dyn_cb->rw = rw;
>      dyn_cb->inline_insn.op = op;
> @@ -431,9 +436,14 @@ void qemu_plugin_flush_cb(void)
>      plugin_cb__simple(QEMU_PLUGIN_EV_FLUSH);
>  }
>  
> -void exec_inline_op(struct qemu_plugin_dyn_cb *cb)
> +void exec_inline_op(struct qemu_plugin_dyn_cb *cb, int cpu_index)
>  {
> -    uint64_t *val = cb->userp;
> +    char *ptr = cb->userp;
> +    if (!cb->inline_direct_ptr) {
> +        ptr = *(char **) cb->userp;
> +    }
> +    ptr += cb->inline_offset;
> +    uint64_t *val = (uint64_t *)(ptr + cpu_index * cb->inline_element_size);
>  
>      switch (cb->inline_insn.op) {
>      case QEMU_PLUGIN_INLINE_ADD_U64:
> @@ -466,7 +476,7 @@ void qemu_plugin_vcpu_mem_cb(CPUState *cpu, uint64_t vaddr,
>                             vaddr, cb->userp);
>              break;
>          case PLUGIN_CB_INLINE:
> -            exec_inline_op(cb);
> +            exec_inline_op(cb, cpu->cpu_index);
>              break;
>          default:
>              g_assert_not_reached();
> diff --git a/plugins/plugin.h b/plugins/plugin.h
> index 5eb2fdbc85e..2c278379b70 100644
> --- a/plugins/plugin.h
> +++ b/plugins/plugin.h
> @@ -66,7 +66,9 @@ struct qemu_plugin_ctx *plugin_id_to_ctx_locked(qemu_plugin_id_t id);
>  
>  void plugin_register_inline_op(GArray **arr,
>                                 enum qemu_plugin_mem_rw rw,
> -                               enum qemu_plugin_op op, void *ptr,
> +                               enum qemu_plugin_op op,
> +                               void *ptr, size_t offset, size_t element_size,
> +                               bool direct_ptr,
>                                 uint64_t imm);
>  
>  void plugin_reset_uninstall(qemu_plugin_id_t id,
> @@ -95,6 +97,6 @@ void plugin_register_vcpu_mem_cb(GArray **arr,
>                                   enum qemu_plugin_mem_rw rw,
>                                   void *udata);
>  
> -void exec_inline_op(struct qemu_plugin_dyn_cb *cb);
> +void exec_inline_op(struct qemu_plugin_dyn_cb *cb, int cpu_index);
>  
>  #endif /* PLUGIN_H */

-- 
Alex Bennée
Virtualisation Tech Lead @ Linaro