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

[Barry Song]

On Fri, Sep 18, 2026 at 2:14 PM Christophe Leroy (CS GROUP)
<chleroy@xxxxxxxxxx> wrote:
>
>
>
> Le 17/09/2026 à 07:29, Wen Jiang a écrit :
> > From: Wen Jiang <jiangwen6@xxxxxxxxxx>
> >
> > 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"

>
> >
> > 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 <jiangwen6@xxxxxxxxxx>
>
> Reviewed-by: Christophe Leroy (CS GROUP) <chleroy@xxxxxxxxxx>

Best Regards
Barry