[Xen-devel] pagetable pinning question

[Christian L. <ch...@pi...>]

Hi!

I want to use pinning for the L1/L2 pagetables.  The currently activated
pagetable maps itself and that works great.  But I (or rather whoever wrote
the pagetable code) also wants to map inactive pagetables and this doesn't
work because of the following check in get_twisted_l2_table:
    if ( (l2v >> PAGE_SHIFT) != entry_pfn )
    {
        MEM_LOG("L2 tables may not map _other_ L2 tables!\n");

Are there counting or protection issues why this is disallowed or was it
just not needed for Linux/Windows?

I guess a work around would be to switch to the inactive pagetable and
switch back when the mapping is no longer needed...

    christian