Re: [Xen-devel] [PATCH v5 1/8] xen: move XENMAPSPACE_grant_table code into grant_table.c

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 08.09.17 at 08:56, <jgross@xxxxxxxx> wrote:
> --- a/xen/arch/x86/mm.c
> +++ b/xen/arch/x86/mm.c
> @@ -4631,40 +4631,19 @@ int xenmem_add_to_physmap_one(
>  {
>      struct page_info *page = NULL;
>      unsigned long gfn = 0; /* gcc ... */
> -    unsigned long prev_mfn, mfn = 0, old_gpfn;
> +    unsigned long prev_mfn, old_gpfn;
>      int rc = 0;
> +    mfn_t mfn = INVALID_MFN;
>      p2m_type_t p2mt;
>  
>      switch ( space )
>      {
>          case XENMAPSPACE_shared_info:
>              if ( idx == 0 )
> -                mfn = virt_to_mfn(d->shared_info);
> +                mfn = _mfn(virt_to_mfn(d->shared_info));
>              break;
>          case XENMAPSPACE_grant_table:
> -            grant_write_lock(d->grant_table);
> -
> -            if ( d->grant_table->gt_version == 0 )
> -                d->grant_table->gt_version = 1;
> -
> -            if ( d->grant_table->gt_version == 2 &&
> -                 (idx & XENMAPIDX_grant_table_status) )
> -            {
> -                idx &= ~XENMAPIDX_grant_table_status;
> -                if ( idx < nr_status_frames(d->grant_table) )
> -                    mfn = virt_to_mfn(d->grant_table->status[idx]);
> -            }
> -            else
> -            {
> -                if ( (idx >= nr_grant_frames(d->grant_table)) &&
> -                     (idx < max_grant_frames) )
> -                    gnttab_grow_table(d, idx + 1);
> -
> -                if ( idx < nr_grant_frames(d->grant_table) )
> -                    mfn = virt_to_mfn(d->grant_table->shared_raw[idx]);
> -            }
> -
> -            grant_write_unlock(d->grant_table);
> +            gnttab_map_frame(d, idx, gpfn, &mfn);

You're ignoring a possible error here. Of course right now this can
only come together with mfn staying INVALID_MFN, but if any
further change to the function happened this may change without
the author noticing that the error check here is missing.

Jan


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