[Xen-devel] Comment & code inconsistency?

["陈诚" <concretechen@xxxxxxxxx>]

Hi all,
    in arch_init_memory() we have the following code:

    ...

    /* Any areas not specified as RAM by the e820 map are considered I/O. */
    for ( i = 0, pfn = 0; pfn < max_page; i++ )
    {
        while ( (i < e820.nr_map) && (e820.map[i].type != E820_RAM) )
            i++;

        if ( i >= e820.nr_map )
        {
            /* No more RAM regions: mark as I/O right to end of memory map. */
            rstart_pfn = rend_pfn = max_page;
        }
        else
        {
            /* Mark as I/O just up as far as next RAM region. */
            rstart_pfn = min_t(unsigned long, max_page,
                               PFN_UP(e820.map[i].addr));
            rend_pfn   = max_t(unsigned long, rstart_pfn,
                               PFN_DOWN(e820.map[i].addr + e820.map[i].size));
        }

        /* Mark as I/O up to next RAM region. */
        for ( ; pfn < rstart_pfn; pfn++ )
        {
            BUG_ON(!mfn_valid(pfn));
            share_xen_page_with_guest(
                mfn_to_page(pfn), dom_io, XENSHARE_writable);
        }

        /* Skip the RAM region. */
        pfn = rend_pfn;
    }

    ...

    it seems that the while loop skips all the areas that are not
specified as RAM and the areas which are specified as RAM are
considered I/O, which contradicts with the comment, or do I
misunderstand this piece of code?

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel