powerpc/mm: Move setting PTE specific flags to pfn_pmd()

powerpc used to set the PTE specific flags in set_pte_at(). That is
different from other architectures. To be consistent with other
architectures powerpc updated pfn_pte() to set _PAGE_PTE in commit
379c926d6334 ("powerpc/mm: move setting pte specific flags to
pfn_pte")

That commit didn't do the same for pfn_pmd() because we expect
pmd_mkhuge() to do that. But as per Linus that is a bad rule:

  The rule that you must use "pmd_mkhuge()" seems _completely_ wrong.
  The only valid use to ever make a pmd out of a pfn is to make a
  huge-page.

Hence update pfn_pmd() to set _PAGE_PTE.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20201022091115.39568-1-aneesh.kumar@linux.ibm.com

1 files changed, 7 insertions, 1 deletions

diff --git a/arch/powerpc/mm/book3s64/pgtable.c b/arch/powerpc/mm/book3s64/pgtable.c
index e18ae50a275c..5b3a3bae21aa 100644
--- a/arch/powerpc/mm/book3s64/pgtable.c
+++ b/arch/powerpc/mm/book3s64/pgtable.c
@@ -136,12 +136,18 @@ static pmd_t pmd_set_protbits(pmd_t pmd, pgprot_t pgprot)
 	return __pmd(pmd_val(pmd) | pgprot_val(pgprot));
 }
 
+/*
+ * At some point we should be able to get rid of
+ * pmd_mkhuge() and mk_huge_pmd() when we update all the
+ * other archs to mark the pmd huge in pfn_pmd()
+ */
 pmd_t pfn_pmd(unsigned long pfn, pgprot_t pgprot)
 {
 	unsigned long pmdv;
 
 	pmdv = (pfn << PAGE_SHIFT) & PTE_RPN_MASK;
-	return pmd_set_protbits(__pmd(pmdv), pgprot);
+
+	return __pmd_mkhuge(pmd_set_protbits(__pmd(pmdv), pgprot));
 }
 
 pmd_t mk_pmd(struct page *page, pgprot_t pgprot)