Re: [PATCH v7 6/6] memory: Introduce address_space_to_flatview_rcu()

[Peter Xu <peterx@redhat.com>]

On Fri, Mar 10, 2023 at 10:24:25AM +0800, Chuang Xu wrote:
> In last patch, we wrap vm_load with begin/commit, here we introduce
> address_space_to_flatview_rcu() to avoid unnecessary enforce commit
> during vm_load.
> 
> Signed-off-by: Chuang Xu <xuchuangxclwt@bytedance.com>
> ---
>  include/exec/memory-internal.h |  2 +-
>  include/exec/memory.h          | 20 ++++++++++++++++++++
>  softmmu/memory.c               |  2 +-
>  3 files changed, 22 insertions(+), 2 deletions(-)
> 
> diff --git a/include/exec/memory-internal.h b/include/exec/memory-internal.h
> index 100c1237ac..1432240449 100644
> --- a/include/exec/memory-internal.h
> +++ b/include/exec/memory-internal.h
> @@ -30,7 +30,7 @@ static inline AddressSpaceDispatch *flatview_to_dispatch(FlatView *fv)
>  
>  static inline AddressSpaceDispatch *address_space_to_dispatch(AddressSpace *as)
>  {
> -    return flatview_to_dispatch(address_space_to_flatview(as));
> +    return flatview_to_dispatch(address_space_to_flatview_rcu(as));
>  }

I'm not sure whether this one is always safe.

tcg_commit() seems to be safe, but maybe address_space_translate_iommu() is
not?  Maybe easier to leave this untouched?

>  
>  FlatView *address_space_get_flatview(AddressSpace *as);
> diff --git a/include/exec/memory.h b/include/exec/memory.h
> index d6fd89db64..235e3017bc 100644
> --- a/include/exec/memory.h
> +++ b/include/exec/memory.h
> @@ -1100,6 +1100,9 @@ bool memory_region_transaction_in_progress(void);
>  
>  void memory_region_transaction_do_commit(void);
>  
> +/*
> + * We recommend using this by default.
> + */

I think this comment doesn't really help.. drop it?

>  static inline FlatView *address_space_to_flatview(AddressSpace *as)

-- 
Peter Xu