On 15.11.2024 10:09, Jan Beulich wrote:
> 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.
I think I now can: memnodemap is set using vmap_contig(). The VESA frame buffer
unmap, neglecting to check VA alignment, will have wrongly unmapped memnodemap.
Jan
