Re: [PATCH 3/6] xen/grant-table: Support mappings required by blkback

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Thu, Oct 20, 2011 at 11:35:54AM -0400, Daniel De Graaf wrote:
> Allow mappings without GNTMAP_contains_pte and allow unmapping to
> specify if the PTEs should be cleared.
> 
> Signed-off-by: Daniel De Graaf <dgdegra@tycho.nsa.gov>
> ---
>  drivers/xen/gntdev.c      |    3 ++-
>  drivers/xen/grant-table.c |   23 ++++-------------------
>  include/xen/grant_table.h |    2 +-
>  3 files changed, 7 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
> index 3987132..5227506 100644
> --- a/drivers/xen/gntdev.c
> +++ b/drivers/xen/gntdev.c
> @@ -312,7 +312,8 @@ static int __unmap_grant_pages(struct grant_map *map, int offset, int pages)
>  		}
>  	}
>  
> -	err = gnttab_unmap_refs(map->unmap_ops + offset, map->pages + offset, pages);
> +	err = gnttab_unmap_refs(map->unmap_ops + offset, map->pages + offset,
> +	                        pages, true);
>  	if (err)
>  		return err;
>  
> diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
> index bf1c094..a02d139 100644
> --- a/drivers/xen/grant-table.c
> +++ b/drivers/xen/grant-table.c
> @@ -472,24 +472,9 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
>  				(map_ops[i].host_addr & ~PAGE_MASK));
>  			mfn = pte_mfn(*pte);
>  		} else {
> -			/* If you really wanted to do this:
> -			 * mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
> -			 *
> -			 * The reason we do not implement it is b/c on the
> -			 * unmap path (gnttab_unmap_refs) we have no means of
> -			 * checking whether the page is !GNTMAP_contains_pte.

Can you mention how you are addressing the !GNTMAP_contains_pte on unmap issue?
(or how it is already addressed).

> -			 *
> -			 * That is without some extra data-structure to carry
> -			 * the struct page, bool clear_pte, and list_head next
> -			 * tuples and deal with allocation/delallocation, etc.
> -			 *
> -			 * The users of this API set the GNTMAP_contains_pte
> -			 * flag so lets just return not supported until it
> -			 * becomes neccessary to implement.
> -			 */
> -			return -EOPNOTSUPP;
> +			mfn = PFN_DOWN(map_ops[i].dev_bus_addr);
>  		}
> -		ret = m2p_add_override(mfn, pages[i], &kmap_ops[i]);
> +		ret = m2p_add_override(mfn, pages[i], kmap_ops ? &kmap_ops[i] : NULL);
>  		if (ret)
>  			return ret;
>  	}
> @@ -499,7 +484,7 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
>  EXPORT_SYMBOL_GPL(gnttab_map_refs);
>  
>  int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
> -		struct page **pages, unsigned int count)
> +		struct page **pages, unsigned int count, bool clear_pte)
>  {
>  	int i, ret;
>  
> @@ -511,7 +496,7 @@ int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
>  		return ret;
>  
>  	for (i = 0; i < count; i++) {
> -		ret = m2p_remove_override(pages[i], true /* clear the PTE */);
> +		ret = m2p_remove_override(pages[i], clear_pte);
>  		if (ret)
>  			return ret;
>  	}
> diff --git a/include/xen/grant_table.h b/include/xen/grant_table.h
> index 11e2dfc..37da54d 100644
> --- a/include/xen/grant_table.h
> +++ b/include/xen/grant_table.h
> @@ -158,6 +158,6 @@ int gnttab_map_refs(struct gnttab_map_grant_ref *map_ops,
>  			struct gnttab_map_grant_ref *kmap_ops,
>  		    struct page **pages, unsigned int count);
>  int gnttab_unmap_refs(struct gnttab_unmap_grant_ref *unmap_ops,
> -		      struct page **pages, unsigned int count);
> +		      struct page **pages, unsigned int count, bool clear_pte);
>  
>  #endif /* __ASM_GNTTAB_H__ */
> -- 
> 1.7.6.4
> 
> 
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