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

[Paolo Bonzini]

On 12/23/22 15:23, Chuang Xu wrote:
>   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);
>   }

This is not valid because the transaction could happen in *another* 
thread.  In that case memory_region_transaction_depth() will be > 0, but 
RCU is needed.

Paolo