Re: [PATCH v4 5/7] xen/arm: introduce GNTTABOP_cache_flush

[Julien Grall <julien.grall@linaro.org>]

Hi Stefano,

On 10/10/2014 12:43, Stefano Stabellini wrote:
> +static int __gnttab_cache_flush(gnttab_cache_flush_t *cflush)
> +{
> +    struct domain *d, *owner;
> +    struct page_info *page;
> +    uint64_t mfn;
> +    void *v;
> +
> +    if ( (cflush->offset >= PAGE_SIZE) ||
> +         (cflush->length > PAGE_SIZE) ||
> +         (cflush->offset + cflush->length > PAGE_SIZE) )
> +        return -EINVAL;
> +
> +    if ( cflush->length == 0 || cflush->op == 0 )
> +        return 0;
> +
> +    /* currently unimplemented */
> +    if ( cflush->op & GNTTAB_CACHE_SOURCE_GREF )
> +        return -EOPNOTSUPP;

I may have miss a part of the discussion. What is the purpose of 
introducing a flag that is not supported? Do we expect to implement on 
Xen 4.6?

-- 
Julien Grall