Re: [Qemu-stable] [PATCH 3/7] address_space_write: address_space_to_flatview needs RCU lock

[Alexey Kardashevskiy]

On 05/03/18 19:36, Paolo Bonzini wrote:
> address_space_write is calling address_space_to_flatview but it can
> be called outside the RCU lock.  To fix it, push the rcu_read_lock/unlock
> pair up from flatview_write to address_space_write.
> 
> Cc: address@hidden

Reviewed-by: Alexey Kardashevskiy <address@hidden>


> Signed-off-by: Paolo Bonzini <address@hidden>
> ---
>  exec.c | 37 ++++++++++++++++++++++---------------
>  1 file changed, 22 insertions(+), 15 deletions(-)
> 
> diff --git a/exec.c b/exec.c
> index e8d7b335b6..0b74b58d45 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -3074,6 +3074,7 @@ static MemTxResult flatview_write_continue(FlatView 
> *fv, hwaddr addr,
>      return result;
>  }
>  
> +/* Called from RCU critical section.  */
>  static MemTxResult flatview_write(FlatView *fv, hwaddr addr, MemTxAttrs 
> attrs,
>                                    const uint8_t *buf, int len)
>  {
> @@ -3082,25 +3083,14 @@ static MemTxResult flatview_write(FlatView *fv, 
> hwaddr addr, MemTxAttrs attrs,
>      MemoryRegion *mr;
>      MemTxResult result = MEMTX_OK;
>  
> -    if (len > 0) {
> -        rcu_read_lock();
> -        l = len;
> -        mr = flatview_translate(fv, addr, &addr1, &l, true);
> -        result = flatview_write_continue(fv, addr, attrs, buf, len,
> -                                         addr1, l, mr);
> -        rcu_read_unlock();
> -    }
> +    l = len;
> +    mr = flatview_translate(fv, addr, &addr1, &l, true);
> +    result = flatview_write_continue(fv, addr, attrs, buf, len,
> +                                     addr1, l, mr);
>  
>      return result;
>  }
>  
> -MemTxResult address_space_write(AddressSpace *as, hwaddr addr,
> -                                              MemTxAttrs attrs,
> -                                              const uint8_t *buf, int len)
> -{
> -    return flatview_write(address_space_to_flatview(as), addr, attrs, buf, 
> len);
> -}
> -
>  /* Called within RCU critical section.  */
>  MemTxResult flatview_read_continue(FlatView *fv, hwaddr addr,
>                                     MemTxAttrs attrs, uint8_t *buf,
> @@ -3209,6 +3199,23 @@ MemTxResult address_space_rw(AddressSpace *as, hwaddr 
> addr,
>                         addr, attrs, buf, len, is_write);
>  }
>  
> +MemTxResult address_space_write(AddressSpace *as, hwaddr addr,
> +                                MemTxAttrs attrs,
> +                                const uint8_t *buf, int len)
> +{
> +    MemTxResult result = MEMTX_OK;
> +    FlatView *fv;
> +
> +    if (len > 0) {
> +        rcu_read_lock();
> +        fv = address_space_to_flatview(as);
> +        result = flatview_write(fv, addr, attrs, buf, len);
> +        rcu_read_unlock();
> +    }
> +
> +    return result;
> +}
> +
>  void cpu_physical_memory_rw(hwaddr addr, uint8_t *buf,
>                              int len, int is_write)
>  {
> 


-- 
Alexey