On Sat, 17 Feb 2024 at 13:51, Borislav Petkov <bp@xxxxxxxxx> wrote:
>
> On Tue, Feb 13, 2024 at 01:41:46PM +0100, Ard Biesheuvel wrote:
> > @@ -201,25 +201,19 @@ unsigned long __head __startup_64(unsigned long physaddr,
> > load_delta += sme_get_me_mask();
> >
> > /* Fixup the physical addresses in the page table */
> > -
> > - pgd = fixup_pointer(early_top_pgt, physaddr);
> > - p = pgd + pgd_index(__START_KERNEL_map);
> > - if (la57)
> > - *p = (unsigned long)level4_kernel_pgt;
> > - else
> > - *p = (unsigned long)level3_kernel_pgt;
> > - *p += _PAGE_TABLE_NOENC - __START_KERNEL_map + load_delta;
> > -
> > if (la57) {
> > - p4d = fixup_pointer(level4_kernel_pgt, physaddr);
> > - p4d[511] += load_delta;
> > + p4d = (p4dval_t *)&RIP_REL_REF(level4_kernel_pgt);
> > + p4d[MAX_PTRS_PER_P4D - 1] += load_delta;
> > }
> >
> > - pud = fixup_pointer(level3_kernel_pgt, physaddr);
> > - pud[510] += load_delta;
> > - pud[511] += load_delta;
> > + pud = &RIP_REL_REF(level3_kernel_pgt)->pud;
> > + pud[PTRS_PER_PUD - 2] += load_delta;
> > + pud[PTRS_PER_PUD - 1] += load_delta;
> > +
> > + pgd = &RIP_REL_REF(early_top_pgt)->pgd;
>
> Let's do the pgd assignment above, where it was so that we have that
> natural order of p4d -> pgd -> pud ->pmd etc manipulations.
>
pud and p4d need to be assigned first, unless we want to keep taking
the addresses of level4_kernel_pgt and level3_kernel_pgt twice as
before.
> > + pgd[PTRS_PER_PGD - 1] = (pgdval_t)(la57 ? p4d : pud) | _PAGE_TABLE_NOENC;
>
> I see what you mean with pgd_index(__START_KERNEL_map) always being 511
> but this:
>
> pgd[pgd_index(__START_KERNEL_map)] = (pgdval_t)(la57 ? p4d : pud) | _PAGE_TABLE_NOENC;
>
> says exactly what gets mapped there in the pagetable while
>
> PTRS_PER_PGD - 1
>
> makes me wonder what's that last pud supposed to map.
>
Fair enough. But the same applies to p4d[] and pud[].
> Other than that, my gut feeling right now is, this would need extensive
> testing so that we make sure there's no fallout from it.
>
More testing is always good, but I am not particularly nervous about
these changes.
I could split this up into 3+ patches so we could bisect any resulting
issues more effectively.
