Re: [Xen-devel] [PATCH v6 02/12] xen: move XENMAPSPACE_grant_table code into grant_table.c

[Julien Grall <julien.grall@xxxxxxx>]

Hi Juergen,

On 13/09/17 16:46, Juergen Gross wrote:
> diff --git a/xen/common/grant_table.c b/xen/common/grant_table.c
> index 00ff075bd9..a462ea7905 100644
> --- a/xen/common/grant_table.c
> +++ b/xen/common/grant_table.c
> @@ -3608,6 +3608,44 @@ int mem_sharing_gref_to_gfn(struct grant_table *gt, 
> grant_ref_t ref,
>   }
>   #endif
>   
> +int gnttab_map_frame(struct domain *d, unsigned long idx, gfn_t gfn,
> +                     mfn_t *mfn)
> +{
> +    int rc = 0;
> +    struct grant_table *gt = d->grant_table;
> +
> +    grant_write_lock(gt);
> +
> +    if ( gt->gt_version == 0 )
> +        gt->gt_version = 1;
> +
> +    if ( gt->gt_version == 2 &&
> +         (idx & XENMAPIDX_grant_table_status) )
> +    {
> +        idx &= ~XENMAPIDX_grant_table_status;
> +        if ( idx < nr_status_frames(gt) )
> +            *mfn = _mfn(virt_to_mfn(gt->status[idx]));
> +        else
> +            rc = -EINVAL;
> +    }
> +    else
> +    {
> +        if ( (idx >= nr_grant_frames(gt)) && (idx < max_grant_frames) )
> +            gnttab_grow_table(d, idx + 1);
> +
> +        if ( idx < nr_grant_frames(gt) )
> +            *mfn = _mfn(virt_to_mfn(gt->shared_raw[idx]));
> +        else
> +            rc = -EINVAL;
> +    }
> +
> +    gnttab_set_frame_gfn(d, idx, gfn);
This code is slightly different compare to the ARM implementation. The 
gfn is now set even if the rc is non-zero (i.e invalid MFN on the ARM 
implementation).
So I think you need to protect gnttab_set_frame_gfn with if ( !rc ).

Cheers,

--
Julien Grall

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