Re: [Xen-devel] [PATCH 18/20] PVH xen: Add and remove foreign pages

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 15.05.13 at 02:52, Mukesh Rathor <mukesh.rathor@xxxxxxxxxx> wrote:
> @@ -695,11 +697,37 @@ long do_memory_op(unsigned long cmd, 
> XEN_GUEST_HANDLE_PARAM(void) arg)
>  
>          domain_lock(d);
>  
> -        page = get_page_from_gfn(d, xrfp.gpfn, NULL, P2M_ALLOC);
> -        if ( page )
> +        /*
> +         * if PVH, the gfn could be mapped to a mfn from foreign domain by 
> the
> +         * user space tool during domain creation. We need to check for that,
> +         * free it up from the p2m, and release refcnt on it. In such a case,
> +         * page would be NULL and the following call would not have refcnt'd
> +         * the page. See also xenmem_add_foreign_to_pmap().
> +         */
> +        page = get_page_from_gfn(d, xrfp.gpfn, &p2mt, P2M_ALLOC);
> +
> +        if ( page || p2m_is_foreign(p2mt) )
>          {
> -            guest_physmap_remove_page(d, xrfp.gpfn, page_to_mfn(page), 0);
> -            put_page(page);
> +            if ( page )
> +                mfn = page_to_mfn(page);
> +            else
> +            {
> +                mfn = mfn_x(get_gfn_query(d, xrfp.gpfn, &tp));
> +                foreign_dom = page_get_owner(mfn_to_page(mfn));
> +                ASSERT(is_pvh_domain(d));
> +                ASSERT(d != foreign_dom);
> +                ASSERT(p2m_is_foreign(tp));

A guest can perform this operation on itself, so I'm afraid none of
the assertions are really valid (they likely will all need to become
error returns).

> +            }
> +
> +            guest_physmap_remove_page(d, xrfp.gpfn, mfn, 0);
> +            if (page)

Coding style flaws have greatly reduced in the series up to here,
but there are still a few cases left. I'm not going to point them out
individually, I really expect you to go through your patches and
fix them.

Jan


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