[PATCH v9 02/10] powerpc/8xx: add pte_set_huge()

vmap installs PTE-level block mappings (SZ_16K/SZ_512K on powerpc/8xx)
by reusing set_huge_pte_at(), a HugeTLB helper gated by
CONFIG_HUGETLB_PAGE. This makes the feature silently unavailable on
CONFIG_HUGETLB_PAGE=n kernels and couples mm/vmalloc.c to HugeTLB
internals it does not otherwise need.

Add pte_set_huge() to powerpc/8xx, next to the existing
pmd_clear_huge()/pud_clear_huge() in mm/nohash/8xx.c. It builds the huge
PTE and writes it into the backing cells directly, without going through
set_huge_pte_at(), so it does not depend on CONFIG_HUGETLB_PAGE.

No pte_clear_huge() is needed: 8xx does not implement
arch_vmap_pte_range_unmap_size(), so the vmap unmap path never takes the
PTE-clearing branch.

In practice PPC_8xx selects HUGETLBFS unconditionally, so
CONFIG_HUGETLB_PAGE=n does not occur there today; this is a decoupling
cleanup rather than a new configuration.

There is no caller yet: mm/vmalloc.c is converted later in this series,
once the generic fallbacks are in place.

Signed-off-by: Wen Jiang <redacted>
Reviewed-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
---
 arch/powerpc/include/asm/nohash/32/pte-8xx.h |  4 +++
 arch/powerpc/mm/nohash/8xx.c                 | 29 ++++++++++++++++++++
 2 files changed, 33 insertions(+)

diff --git a/arch/powerpc/include/asm/nohash/32/pte-8xx.h b/arch/powerpc/include/asm/nohash/32/pte-8xx.h
index e2ea8ba9f8cae..1ee3f8f0de974 100644
--- a/arch/powerpc/include/asm/nohash/32/pte-8xx.h
+++ b/arch/powerpc/include/asm/nohash/32/pte-8xx.h

@@ -235,6 +235,10 @@ static inline pte_t ptep_get(pte_t *ptep)
 }
 #endif /* CONFIG_PPC_16K_PAGES */
 
+#define __HAVE_ARCH_PTE_SET_HUGE
+void pte_set_huge(pte_t *ptep, unsigned long addr, phys_addr_t phys,
+		  pgprot_t prot, unsigned long size);
+
 #endif
 
 #endif /* __KERNEL__ */

diff --git a/arch/powerpc/mm/nohash/8xx.c b/arch/powerpc/mm/nohash/8xx.c
index a9d3f4729eada..2518d2a6bdb41 100644
--- a/arch/powerpc/mm/nohash/8xx.c
+++ b/arch/powerpc/mm/nohash/8xx.c

@@ -220,3 +220,32 @@ int pmd_clear_huge(pmd_t *pmd)
 {
 	 return 0;
 }
+
+/*
+ * vmap PTE-level block mapping. Sets a present kernel mapping directly,
+ * so unlike set_huge_pte_at() it needs neither CONFIG_HUGETLB_PAGE nor
+ * set_pte_filter() (a no-op for non-exec kernel mappings).
+ */
+void pte_set_huge(pte_t *ptep, unsigned long addr, phys_addr_t phys,
+		  pgprot_t prot, unsigned long size)
+{
+	pmd_t *pmdp = pmd_off(&init_mm, addr);
+	pte_t pte = pfn_pte(PHYS_PFN(phys), prot);
+	pte_basic_t val;
+	pte_basic_t *entry = (pte_basic_t *)ptep;
+	int num, i;
+
+	pte = arch_make_huge_pte(pte, ilog2(size), 0);
+	val = pte_val(pte);
+
+	/*
+	 * Make sure hardware valid bit is not set. We don't do
+	 * tlb flush for this update.
+	 */
+	VM_WARN_ON(pte_hw_valid(*ptep) && !pte_protnone(*ptep));
+
+	num = number_of_cells_per_pte(pmdp, val, 1);
+
+	for (i = 0; i < num; i++, entry++, val += SZ_4K)
+		*entry = val;
+}

-- 
2.34.1