Re: [Xen-devel] [PATCH] x86/mm: Consolidate all Xen L4 slot writing into init_xen_l4_slots()

[Tim Deegan <tim@xxxxxxx>]

At 18:07 +0100 on 01 Sep (1504289261), Andrew Cooper wrote:
>      if ( unlikely(root_pgt_pv_xen_slots < ROOT_PAGETABLE_PV_XEN_SLOTS) )
>      {
> -        l4_pgentry_t *next = &l4tab[ROOT_PAGETABLE_FIRST_XEN_SLOT +
> -                                    root_pgt_pv_xen_slots];
> +        /*
> +         * If using highmem-start=, artificially shorten the directmap to
> +         * simulate very large machines.
> +         */
> +        l4_pgentry_t *next;
> +
> +        memcpy(&l4t[l4_table_offset(XEN_VIRT_START)],
> +               &idle_pg_table[l4_table_offset(XEN_VIRT_START)],
> +               (ROOT_PAGETABLE_FIRST_XEN_SLOT + root_pgt_pv_xen_slots -
> +                l4_table_offset(XEN_VIRT_START)) * sizeof(*l4t));
> +
> +        next = &l4t[ROOT_PAGETABLE_FIRST_XEN_SLOT + root_pgt_pv_xen_slots];
>  
>          if ( l4e_get_intpte(split_l4e) )
>              *next++ = split_l4e;
>  
>          memset(next, 0,
> -               _p(&l4tab[ROOT_PAGETABLE_LAST_XEN_SLOT + 1]) - _p(next));
> +               _p(&l4t[ROOT_PAGETABLE_LAST_XEN_SLOT + 1]) - _p(next));
>      }
> -#else
> -    BUILD_BUG_ON(root_pgt_pv_xen_slots != ROOT_PAGETABLE_PV_XEN_SLOTS);
> +    else
>  #endif
> -    l4tab[l4_table_offset(LINEAR_PT_VIRT_START)] =
> -        l4e_from_pfn(domain_page_map_to_mfn(l4tab), __PAGE_HYPERVISOR_RW);
> -    l4tab[l4_table_offset(PERDOMAIN_VIRT_START)] =
> -        l4e_from_page(d->arch.perdomain_l3_pg, __PAGE_HYPERVISOR_RW);
> -    if ( zap_ro_mpt || is_pv_32bit_domain(d) )
> -        l4tab[l4_table_offset(RO_MPT_VIRT_START)] = l4e_empty();
> +    {
> +        /*
> +         * For PV guests, provide the shortened directmap, up to 
> PV_XEN_SLOTS.
> +         * For HVM guests and the idle vcpus, provide the extended directmap.
> +         */
> +        unsigned int slots = ((d && !paging_mode_external(d))
> +                              ? ROOT_PAGETABLE_PV_XEN_SLOTS
> +                              : ROOT_PAGETABLE_XEN_SLOTS);
> +
> +        memcpy(&l4t[l4_table_offset(XEN_VIRT_START)],
> +               &idle_pg_table[l4_table_offset(XEN_VIRT_START)],
> +               (ROOT_PAGETABLE_FIRST_XEN_SLOT + slots -
> +                l4_table_offset(XEN_VIRT_START)) * sizeof(*l4t));

Does this branch need a memset(0) for the PV case, to zap the higher
directmap slots?  

The shadow changes all look fine, so:
Acked-by: Tim Deegan <tim@xxxxxxx>

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