Re: [Xen-devel] [PATCH v3 2/6] x86/hvm: Provide XEN_DMOP_add_to_physmap

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 12.01.18 at 13:45, <ross.lagerwall@xxxxxxxxxx> wrote:
> --- a/xen/arch/x86/hvm/dm.c
> +++ b/xen/arch/x86/hvm/dm.c
> @@ -640,6 +640,42 @@ static int dm_op(const struct dmop_args *op_args)
>          break;
>      }
>  
> +    case XEN_DMOP_add_to_physmap:
> +    {
> +        struct xen_dm_op_add_to_physmap *data =
> +            &op.u.add_to_physmap;
> +        struct xen_add_to_physmap xatp = {
> +            .domid = op_args->domid,
> +            .size = data->size,
> +            .space = XENMAPSPACE_gmfn_range,
> +            .idx = data->src_gfn,
> +            .gpfn = data->dst_gfn,
> +        };
> +
> +        if ( data->pad )
> +        {
> +            rc = -EINVAL;
> +            break;
> +        }
> +
> +        if ( xatp.size != data->size )
> +        {
> +            rc = -EOVERFLOW;
> +            break;

I guess this is fine for now, but clearly not really necessary, as the
continuation logic could take care of the situation. Please add a
comment to this effect.

> --- a/xen/include/public/hvm/dm_op.h
> +++ b/xen/include/public/hvm/dm_op.h
> @@ -368,6 +368,24 @@ struct xen_dm_op_remote_shutdown {
>                             /* (Other reason values are not blocked) */
>  };
>  
> +/*
> + * XEN_DMOP_add_to_physmap : Sets the GFNs at which a page range appears in
> + *                           the specified guest's address space. Identical 
> to
> + *                           XENMEM_add_to_physmap with
> + *                           space == XENMAPSPACE_gmfn_range.
> + */
> +#define XEN_DMOP_add_to_physmap 17
> +
> +struct xen_dm_op_add_to_physmap {
> +    /* Number of GFNs to process. */
> +    uint32_t size;
> +    uint32_t pad;
> +    /* Starting GFN of the source mapping page(s). */
> +    uint64_aligned_t src_gfn;
> +    /* Starting GFN where the source mapping page(s) should appear. */
> +    uint64_aligned_t dst_gfn;
> +};

So why again is this "add-to-physmap"? It's moving memory around,
isn't it? The comment also could be more clear in this regard.
Everything else looks fine to me now.

Jan


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