[RFC PATCH v1 4/4] mm/vmalloc: Add support for huge pages on VMAP and VMALLOC for powerpc 8xx

[Christophe Leroy <christophe.leroy@csgroup.eu>]

powerpc 8xx has 4 page sizes:
- 4k
- 16k
- 512k
- 8M

At the time being, vmalloc and vmap only support huge pages which are
leaf at PMD level.

Here the PMD level is 4M, it doesn't correspond to any supported
page size.

For the time being, implement use of 16k and 512k pages which is done
at PTE level.

Support of 8M pages will be implemented later, it requires use of
hugepd tables.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
---
 arch/powerpc/Kconfig |  3 +-
 mm/vmalloc.c         | 74 ++++++++++++++++++++++++++++++++++++++------
 2 files changed, 66 insertions(+), 11 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 27e88c38fdf7..b443716f7413 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -188,7 +188,8 @@ config PPC
 	select GENERIC_TIME_VSYSCALL
 	select GENERIC_VDSO_TIME_NS
 	select HAVE_ARCH_AUDITSYSCALL
-	select HAVE_ARCH_HUGE_VMAP		if PPC_BOOK3S_64 && PPC_RADIX_MMU
+	select HAVE_ARCH_HUGE_VMAP		if (PPC_BOOK3S_64 && PPC_RADIX_MMU) || PPC_8xx
+	select HAVE_ARCH_HUGE_VMALLOC		if PPC_8xx
 	select HAVE_ARCH_JUMP_LABEL
 	select HAVE_ARCH_JUMP_LABEL_RELATIVE
 	select HAVE_ARCH_KASAN			if PPC32 && PPC_PAGE_SHIFT <= 14
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 5d96fee17226..1f9f9be8ec01 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -36,6 +36,7 @@
 #include <linux/overflow.h>
 #include <linux/pgtable.h>
 #include <linux/uaccess.h>
+#include <linux/hugetlb.h>
 #include <asm/tlbflush.h>
 #include <asm/shmparam.h>
 
@@ -81,12 +82,55 @@ static void free_work(struct work_struct *w)
 }
 
 /*** Page table manipulation functions ***/
+static int vmap_try_huge_pte(pte_t *ptep, unsigned long addr, unsigned long end,
+			     u64 pfn, pgprot_t prot, unsigned int max_page_shift)
+{
+	unsigned long size = end - addr;
+	pte_t pte;
+
+	if (!IS_ENABLED(CONFIG_PPC_8xx))
+		return 0;
+
+	if (PAGE_SIZE == SZ_16K && size < SZ_512K)
+		return 0;
+
+	if (size < SZ_16K)
+		return 0;
+
+	if (max_page_shift < 14)
+		return 0;
+
+	if (size > SZ_512K)
+		size = SZ_512K;
+
+	if (max_page_shift < 19 && size > SZ_16K)
+		size = SZ_16K;
+
+	if (!IS_ALIGNED(addr, size))
+		return 0;
+
+	if (!IS_ALIGNED(PFN_PHYS(pfn), size))
+		return 0;
+
+	if (pte_present(*ptep))
+		return 0;
+
+	pte = pfn_pte(pfn, prot);
+	pte = pte_mkhuge(pte);
+	pte = arch_make_huge_pte(pte, ilog2(size), 0);
+
+	set_huge_pte_at(&init_mm, addr, ptep, pte);
+
+	return PFN_DOWN(size);
+}
+
 static int vmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 			phys_addr_t phys_addr, pgprot_t prot,
-			pgtbl_mod_mask *mask)
+			unsigned int max_page_shift, pgtbl_mod_mask *mask)
 {
 	pte_t *pte;
 	u64 pfn;
+	int npages;
 
 	pfn = phys_addr >> PAGE_SHIFT;
 	pte = pte_alloc_kernel_track(pmd, addr, mask);
@@ -94,9 +138,14 @@ static int vmap_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end,
 		return -ENOMEM;
 	do {
 		BUG_ON(!pte_none(*pte));
-		set_pte_at(&init_mm, addr, pte, pfn_pte(pfn, prot));
-		pfn++;
-	} while (pte++, addr += PAGE_SIZE, addr != end);
+
+		npages = vmap_try_huge_pte(pte, addr, end, pfn, prot, max_page_shift);
+		if (!npages) {
+			set_pte_at(&init_mm, addr, pte, pfn_pte(pfn, prot));
+			npages = 1;
+		}
+		pfn += npages;
+	} while (pte += npages, addr += PAGE_SIZE * npages, addr != end);
 	*mask |= PGTBL_PTE_MODIFIED;
 	return 0;
 }
@@ -145,7 +194,7 @@ static int vmap_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
 			continue;
 		}
 
-		if (vmap_pte_range(pmd, addr, next, phys_addr, prot, mask))
+		if (vmap_pte_range(pmd, addr, next, phys_addr, prot, max_page_shift, mask))
 			return -ENOMEM;
 	} while (pmd++, phys_addr += (next - addr), addr = next, addr != end);
 	return 0;
@@ -2881,8 +2930,7 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
 		return NULL;
 	}
 
-	if (vmap_allow_huge && !(vm_flags & VM_NO_HUGE_VMAP) &&
-			arch_vmap_pmd_supported(prot)) {
+	if (vmap_allow_huge && !(vm_flags & VM_NO_HUGE_VMAP)) {
 		unsigned long size_per_node;
 
 		/*
@@ -2895,11 +2943,17 @@ void *__vmalloc_node_range(unsigned long size, unsigned long align,
 		size_per_node = size;
 		if (node == NUMA_NO_NODE)
 			size_per_node /= num_online_nodes();
-		if (size_per_node >= PMD_SIZE) {
+		if (arch_vmap_pmd_supported(prot) && size_per_node >= PMD_SIZE) {
 			shift = PMD_SHIFT;
-			align = max(real_align, 1UL << shift);
-			size = ALIGN(real_size, 1UL << shift);
+		} else if (IS_ENABLED(CONFIG_PPC_8xx)) {
+			if (size_per_node >= SZ_512K) {
+				shift = 19;
+			} else if (size_per_node >= SZ_16K) {
+				shift = 14;
+			}
 		}
+		align = max(real_align, 1UL << shift);
+		size = ALIGN(real_size, 1UL << shift);
 	}
 
 again:
-- 
2.25.0