Re: [RFC v4 2/3] memory: add depth assert in address_space_to_flatview

[Philippe Mathieu-Daudé]

On 23/12/22 15:23, Chuang Xu wrote:
> Before using any flatview, sanity check we're not during a memory
> region transaction or the map can be invalid.
>
> Signed-off-by: Chuang Xu <xuchuangxclwt@bytedance.com>
> ---
>   include/exec/memory.h | 9 +++++++++
>   softmmu/memory.c      | 5 +++++
>   2 files changed, 14 insertions(+)
>
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index 91f8a2395a..66c43b4862 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -1069,8 +1069,17 @@ struct FlatView {
>       MemoryRegion *root;
>   };
>   
> +int memory_region_transaction_get_depth(void);

Do we want to expose this; isn't the depth internal?

If we need to expose something, can we restrict it to

  bool memory_region_in_transaction(void) or
  bool memory_region_transaction_in_progress(void)?

>   static inline FlatView *address_space_to_flatview(AddressSpace *as)
>   {
> +    /*
> +     * Before using any flatview, sanity check we're not during a memory
> +     * region transaction or the map can be invalid.  Note that this can
> +     * also be called during commit phase of memory transaction, but that
> +     * should also only happen when the depth decreases to 0 first.
> +     */
> +    assert(memory_region_transaction_get_depth() == 0 || rcu_read_locked());
>       return qatomic_rcu_read(&as->current_map);
>   }