Re: [PATCH v8 02/10] powerpc/8xx: add pte_set_huge()

On Fri, Sep 18, 2026 at 2:14 PM Christophe Leroy (CS GROUP)
[off-list ref] wrote:

Le 17/09/2026 à 07:29, Wen Jiang a écrit :

quoted

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.

Hi Christophe,

Do you mean the code below? If so, it sounds like a good place to
clean this up for powerpc as a separate cleanup patch.

diff --git a/arch/powerpc/mm/nohash/8xx.c b/arch/powerpc/mm/nohash/8xx.c
index 2518d2a6bdb4..830cdb391161 100644
--- a/arch/powerpc/mm/nohash/8xx.c
+++ b/arch/powerpc/mm/nohash/8xx.c

@@ -87,9 +87,7 @@ static int __ref

__early_map_kernel_hugepage(unsigned long va, phys_addr_t pa,
        if (WARN_ON(!ptep))
                return -ENOMEM;

-       set_huge_pte_at(&init_mm, va, ptep,
-                       arch_make_huge_pte(pfn_pte(pa >> PAGE_SHIFT,
prot), shift, 0),
-                       1UL << shift);
+       pte_set_huge(ptep, va, pa, prot, 1UL << shift);

        return 0;
 }

diff --git a/arch/powerpc/platforms/Kconfig.cputype

b/arch/powerpc/platforms/Kconfig.cputype
index f0adbf7ecb7f..efba4d960083 100644

--- a/arch/powerpc/platforms/Kconfig.cputype
+++ b/arch/powerpc/platforms/Kconfig.cputype

@@ -41,7 +41,6 @@ config PPC_8xx
        select FSL_SOC
        select PPC_KUEP
        select HAVE_ARCH_VMAP_STACK
-       select HUGETLBFS

 config 44x
        bool "AMCC 44x, 46x or 47x"

quoted

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>

Best Regards
Barry