... adding Kirill
On 8/7/20 1:40 AM, Joerg Roedel wrote:
> + lvl = "p4d";
> + p4d = p4d_alloc(&init_mm, pgd, addr);
> + if (!p4d)
> + goto failed;
>
> + /*
> + * With 5-level paging the P4D level is not folded. So the PGDs
> + * are now populated and there is no need to walk down to the
> + * PUD level.
> + */
> if (pgtable_l5_enabled())
> continue;
It's early and I'm a coffee or two short of awake, but I had to stare at
the comment for a but to make sense of it.
It feels wrong, I think, because the 5-level code usually ends up doing
*more* allocations and in this case, it is _appearing_ to do fewer.
Would something like this make sense?
/*
* The goal here is to allocate all possibly required
* hardware page tables pointed to by the top hardware
* level.
*
* On 4-level systems, the p4d layer is folded away and
* the above code does no preallocation. Below, go down
* to the pud _software_ level to ensure the second
* hardware level is allocated.
*/
> - pud = pud_offset(p4d, addr);
> - if (pud_none(*pud)) {
> - /* Ends up here only with 4-level paging */
> - pud = pud_alloc(&init_mm, p4d, addr);
> - if (!pud) {
> - lvl = "pud";
> - goto failed;
> - }
> - }
> + lvl = "pud";
> + pud = pud_alloc(&init_mm, p4d, addr);
> + if (!pud)
> + goto failed;
> }
