powerpc/8xx: rework support for 8M pages using contiguous PTE entries

In order to fit better with standard Linux page tables layout, add support
for 8M pages using contiguous PTE entries in a standard page table.  Page
tables will then be populated with 1024 similar entries and two PMD
entries will point to that page table.

The PMD entries also get a flag to tell it is addressing an 8M page, this
is required for the HW tablewalk assistance.

Link: https://lkml.kernel.org/r/8693d9a0408371043ca63bf9e4a9c140667af63e.1719928057.git.christophe.leroy@csgroup.eu
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Xu <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 18 insertions, 22 deletions

diff --git a/arch/powerpc/mm/nohash/8xx.c b/arch/powerpc/mm/nohash/8xx.c
index d93433e26ded..388bba0ab3e7 100644
--- a/arch/powerpc/mm/nohash/8xx.c
+++ b/arch/powerpc/mm/nohash/8xx.c
@@ -11,6 +11,7 @@
 #include <linux/hugetlb.h>
 
 #include <asm/fixmap.h>
+#include <asm/pgalloc.h>
 
 #include <mm/mmu_decl.h>
 
@@ -48,20 +49,6 @@ unsigned long p_block_mapped(phys_addr_t pa)
 	return 0;
 }
 
-static pte_t __init *early_hugepd_alloc_kernel(hugepd_t *pmdp, unsigned long va)
-{
-	if (hpd_val(*pmdp) == 0) {
-		pte_t *ptep = memblock_alloc(sizeof(pte_basic_t), SZ_4K);
-
-		if (!ptep)
-			return NULL;
-
-		hugepd_populate_kernel((hugepd_t *)pmdp, ptep, PAGE_SHIFT_8M);
-		hugepd_populate_kernel((hugepd_t *)pmdp + 1, ptep, PAGE_SHIFT_8M);
-	}
-	return hugepte_offset(*(hugepd_t *)pmdp, va, PGDIR_SHIFT);
-}
-
 static int __ref __early_map_kernel_hugepage(unsigned long va, phys_addr_t pa,
 					     pgprot_t prot, int psize, bool new)
 {
@@ -75,24 +62,33 @@ static int __ref __early_map_kernel_hugepage(unsigned long va, phys_addr_t pa,
 		if (WARN_ON(slab_is_available()))
 			return -EINVAL;
 
-		if (psize == MMU_PAGE_512K)
+		if (psize == MMU_PAGE_512K) {
 			ptep = early_pte_alloc_kernel(pmdp, va);
-		else
-			ptep = early_hugepd_alloc_kernel((hugepd_t *)pmdp, va);
+			/* The PTE should never be already present */
+			if (WARN_ON(pte_present(*ptep) && pgprot_val(prot)))
+				return -EINVAL;
+		} else {
+			if (WARN_ON(!pmd_none(*pmdp) || !pmd_none(*(pmdp + 1))))
+				return -EINVAL;
+
+			ptep = early_alloc_pgtable(PTE_FRAG_SIZE);
+			pmd_populate_kernel(&init_mm, pmdp, ptep);
+
+			ptep = early_alloc_pgtable(PTE_FRAG_SIZE);
+			pmd_populate_kernel(&init_mm, pmdp + 1, ptep);
+
+			ptep = (pte_t *)pmdp;
+		}
 	} else {
 		if (psize == MMU_PAGE_512K)
 			ptep = pte_offset_kernel(pmdp, va);
 		else
-			ptep = hugepte_offset(*(hugepd_t *)pmdp, va, PGDIR_SHIFT);
+			ptep = (pte_t *)pmdp;
 	}
 
 	if (WARN_ON(!ptep))
 		return -ENOMEM;
 
-	/* The PTE should never be already present */
-	if (new && WARN_ON(pte_present(*ptep) && pgprot_val(prot)))
-		return -EINVAL;
-
 	set_huge_pte_at(&init_mm, va, ptep,
 			pte_mkhuge(pfn_pte(pa >> PAGE_SHIFT, prot)),
 			1UL << mmu_psize_to_shift(psize));