On 14.11.2024 15:57, Roger Pau Monne wrote:
> @@ -5517,7 +5524,8 @@ int map_pages_to_xen(
> L3T_LOCK(current_l3page);
> ol3e = *pl3e;
>
> - if ( cpu_has_page1gb && IS_L3E_ALIGNED(virt, mfn) &&
> + if ( cpu_has_page1gb &&
> + (!(flags & _PAGE_PRESENT) || IS_L3E_ALIGNED(virt, mfn)) &&
> nr_mfns >= (1UL << (L3_PAGETABLE_SHIFT - PAGE_SHIFT)) &&
> !(flags & (_PAGE_PAT | MAP_SMALL_PAGES)) )
> {
> @@ -5636,7 +5644,7 @@ int map_pages_to_xen(
> if ( !pl2e )
> goto out;
>
> - if ( IS_L2E_ALIGNED(virt, mfn) &&
> + if ( (!(flags & _PAGE_PRESENT) || IS_L2E_ALIGNED(virt, mfn)) &&
> (nr_mfns >= (1u << PAGETABLE_ORDER)) &&
> !(flags & (_PAGE_PAT|MAP_SMALL_PAGES)) )
> {
Upon inspecting Andrew's report of crashes I noticed that this can't be quite
right. We can't entirely skip the alignment check when non-present mappings
are requested; we merely need to limit the check to the VA. In a reply to
the 1st v2 I actually had it arranged to match that requirement:
if ( (cpu_has_page1gb || !(flags & _PAGE_PRESENT)) &&
IS_L3E_ALIGNED(virt, flags & _PAGE_PRESENT ? mfn : _mfn(0)) &&
nr_mfns >= (1UL << (L3_PAGETABLE_SHIFT - PAGE_SHIFT)) &&
!(flags & (_PAGE_PAT | MAP_SMALL_PAGES)) )
Yet then I didn't pay attention to the difference when reviewing the 2nd v2
(that versioning issue of course isn't helping here either).
I'm afraid I can't (yet) connect the observed bad behavior with this issue,
though.
Jan
