Re: [PATCH v8 02/10] powerpc/8xx: add pte_set_huge()
From: "Christophe Leroy (CS GROUP)" <chleroy@kernel.org>
Date: 2026-09-18 06:14:50
Also in:
linux-mm, linuxppc-dev, lkml
Le 17/09/2026 à 07:29, Wen Jiang a écrit :
From: Wen Jiang <redacted> 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 block-mapping 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.
8xx selects CONFIG_HUGETLB_PAGE because it uses set_huge_pte_at() to map
kernel text with large pages. That was added by commit 34536d780683
("powerpc/8xx: Add a function to early map kernel via huge pages")
But now pte_set_huge() could be used instead in
__early_map_kernel_hugepage() and then CONFIG_HUGETLB_PAGE could be removed.
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>
quoted hunk ↗ jump to hunk
--- 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; +}