Re: [Xen-devel] [PATCH 12/22] xen/arm: p2m: Remove unnecessary locking

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 20 Jul 2016, Julien Grall wrote:
> The p2m is not yet in use when p2m_init and p2m_allocate_table are
> called. Furthermore the p2m is not used anymore when p2m_teardown is
> called. So taking the p2m lock is not necessary.
> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxx>

Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


>  xen/arch/arm/p2m.c | 14 +-------------
>  1 file changed, 1 insertion(+), 13 deletions(-)
> 
> diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c
> index 2f50b4f..4c279dc 100644
> --- a/xen/arch/arm/p2m.c
> +++ b/xen/arch/arm/p2m.c
> @@ -1267,8 +1267,6 @@ int p2m_alloc_table(struct domain *d)
>      if ( page == NULL )
>          return -ENOMEM;
>  
> -    spin_lock(&p2m->lock);
> -
>      /* Clear both first level pages */
>      for ( i = 0; i < P2M_ROOT_PAGES; i++ )
>          clear_and_clean_page(page + i);
> @@ -1284,8 +1282,6 @@ int p2m_alloc_table(struct domain *d)
>       */
>      flush_tlb_domain(d);
>  
> -    spin_unlock(&p2m->lock);
> -
>      return 0;
>  }
>  
> @@ -1350,8 +1346,6 @@ void p2m_teardown(struct domain *d)
>      struct p2m_domain *p2m = &d->arch.p2m;
>      struct page_info *pg;
>  
> -    spin_lock(&p2m->lock);
> -
>      while ( (pg = page_list_remove_head(&p2m->pages)) )
>          free_domheap_page(pg);
>  
> @@ -1363,8 +1357,6 @@ void p2m_teardown(struct domain *d)
>      p2m_free_vmid(d);
>  
>      radix_tree_destroy(&p2m->mem_access_settings, NULL);
> -
> -    spin_unlock(&p2m->lock);
>  }
>  
>  int p2m_init(struct domain *d)
> @@ -1375,12 +1367,11 @@ int p2m_init(struct domain *d)
>      spin_lock_init(&p2m->lock);
>      INIT_PAGE_LIST_HEAD(&p2m->pages);
>  
> -    spin_lock(&p2m->lock);
>      p2m->vmid = INVALID_VMID;
>  
>      rc = p2m_alloc_vmid(d);
>      if ( rc != 0 )
> -        goto err;
> +        return rc;
>  
>      d->arch.vttbr = 0;
>  
> @@ -1393,9 +1384,6 @@ int p2m_init(struct domain *d)
>      p2m->mem_access_enabled = false;
>      radix_tree_init(&p2m->mem_access_settings);
>  
> -err:
> -    spin_unlock(&p2m->lock);
> -
>      return rc;
>  }
>  
> -- 
> 1.9.1
> 

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