[Xen-devel] Re: [PATCH 06/11] xen: gntdev: move use of GNTMAP_contains_pte next to the map_op

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

On Wed, Dec 15, 2010 at 01:40:41PM +0000, stefano.stabellini@xxxxxxxxxxxxx 
wrote:
> From: Ian Campbell <ian.campbell@xxxxxxxxxx>
> 
> This flag controls the meaning of gnttab_map_grant_ref.host_addr and
> specifies that the field contains a refernce to the pte entry to be
                                      ^^^^^^^^ - reference

> used to perform the mapping. Therefore move the use of this flag to
> the point at which we actually use a reference to the pte instead of
> something else, splitting up the usage of the flag in this way is
> confusing and potentially error prone.
> 
> The other flags are all properties of the mapping itself as opposed to
> properties of the hypercall arguments and therefore it make sense to
> continue to pass them round in map->flags.
> 
> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> Cc: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
> Cc: Stefano Stabellini <Stefano.Stabellini@xxxxxxxxxxxxx>
> Cc: Derek G. Murray <Derek.Murray@xxxxxxxxxxxx>
> Cc: Gerd Hoffmann <kraxel@xxxxxxxxxx>
> Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
> ---
>  drivers/xen/gntdev.c |    8 +++++---
>  1 files changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/xen/gntdev.c b/drivers/xen/gntdev.c
> index cf61c7d..b916d6b 100644
> --- a/drivers/xen/gntdev.c
> +++ b/drivers/xen/gntdev.c
> @@ -205,10 +205,12 @@ static int find_grant_ptes(pte_t *pte, pgtable_t token, 
> unsigned long addr, void
>       BUG_ON(pgnr >= map->count);
>       pte_maddr  = (u64)pfn_to_mfn(page_to_pfn(token)) << PAGE_SHIFT;
>       pte_maddr += (unsigned long)pte & ~PAGE_MASK;
> -     gnttab_set_map_op(&map->map_ops[pgnr], pte_maddr, map->flags,
> +     gnttab_set_map_op(&map->map_ops[pgnr], pte_maddr,
> +                       GNTMAP_contains_pte | map->flags,

Ok, but the gnttab_set_map_op will do the exact thing it did before. It still 
does this:

map->host_addr = addr;

irregardless if you pass in any flag.

>                         map->grants[pgnr].ref,
>                         map->grants[pgnr].domid);
> -     gnttab_set_unmap_op(&map->unmap_ops[pgnr], pte_maddr, map->flags,
> +     gnttab_set_unmap_op(&map->unmap_ops[pgnr], pte_maddr,
> +                         GNTMAP_contains_pte | map->flags,
>                           0 /* handle */);
>       return 0;
>  }
> @@ -579,7 +581,7 @@ static int gntdev_mmap(struct file *flip, struct 
> vm_area_struct *vma)
>       vma->vm_private_data = map;
>       map->vma = vma;
>  
> -     map->flags = GNTMAP_host_map | GNTMAP_application_map | 
> GNTMAP_contains_pte;
> +     map->flags = GNTMAP_host_map | GNTMAP_application_map;
>       if (!(vma->vm_flags & VM_WRITE))
>               map->flags |= GNTMAP_readonly;
>  
> -- 
> 1.5.6.5
> 
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