Re: [RFC 6/9] powerpc/hugetlb: Enable ARCH_WANT_GENERAL_HUGETLB for BOOK3S 64K

From: Rui Teng
Date: Mon Mar 21 2016 - 05:55:51 EST


On 3/9/16 8:10 PM, Anshuman Khandual wrote:
This enables ARCH_WANT_GENERAL_HUGETLB for BOOK3S 64K in Kconfig.
It also implements a new function 'pte_huge' which is required by
function 'huge_pte_alloc' from generic VM. Existing BOOK3S 64K
specific functions 'huge_pte_alloc' and 'huge_pte_offset' (which
are no longer required) are removed with this change.

Signed-off-by: Anshuman Khandual <khandual@xxxxxxxxxxxxxxxxxx>
---
arch/powerpc/Kconfig | 4 ++
arch/powerpc/include/asm/book3s/64/hash-64k.h | 8 ++++
arch/powerpc/mm/hugetlbpage.c | 60 ---------------------------
3 files changed, 12 insertions(+), 60 deletions(-)

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 9faa18c..c6920bb 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -33,6 +33,10 @@ config HAVE_SETUP_PER_CPU_AREA
config NEED_PER_CPU_EMBED_FIRST_CHUNK
def_bool PPC64

+config ARCH_WANT_GENERAL_HUGETLB
+ depends on PPC_64K_PAGES && PPC_BOOK3S_64
+ def_bool y
+
On the source code, the PowerPC specified huge_pte_alloc() function will not be defined if the configure logic is "!PPC_4K_PAGES && PPC_BOOK3S_64", but on the Kconfig file the general huge_pte_alloc() function will only be defined if the logic is "PPC_64K_PAGES && PPC_BOOK3S_64".

It works if PPC_4K_PAGES and PPC_64K_PAGES always against each other, but I also find PPC_16K_PAGES and PPC_256K_PAGES on the same Kconfig file. What happens if we configure PPC_16K_PAGES instead of PPC_4K_PAGES?

config NR_IRQS
int "Number of virtual interrupt numbers"
range 32 32768
diff --git a/arch/powerpc/include/asm/book3s/64/hash-64k.h b/arch/powerpc/include/asm/book3s/64/hash-64k.h
index 849bbec..5e9b9b9 100644
--- a/arch/powerpc/include/asm/book3s/64/hash-64k.h
+++ b/arch/powerpc/include/asm/book3s/64/hash-64k.h
@@ -143,6 +143,14 @@ extern bool __rpte_sub_valid(real_pte_t rpte, unsigned long index);
* Defined in such a way that we can optimize away code block at build time
* if CONFIG_HUGETLB_PAGE=n.
*/
+static inline int pte_huge(pte_t pte)
+{
+ /*
+ * leaf pte for huge page
+ */
+ return !!(pte_val(pte) & _PAGE_PTE);
+}
+
static inline int pmd_huge(pmd_t pmd)
{
/*
diff --git a/arch/powerpc/mm/hugetlbpage.c b/arch/powerpc/mm/hugetlbpage.c
index f834a74..f6e4712 100644
--- a/arch/powerpc/mm/hugetlbpage.c
+++ b/arch/powerpc/mm/hugetlbpage.c
@@ -59,42 +59,7 @@ pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
/* Only called for hugetlbfs pages, hence can ignore THP */
return __find_linux_pte_or_hugepte(mm->pgd, addr, NULL, NULL);
}
-#else
-pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
-{
- pgd_t pgd, *pgdp;
- pud_t pud, *pudp;
- pmd_t pmd, *pmdp;
-
- pgdp = mm->pgd + pgd_index(addr);
- pgd = READ_ONCE(*pgdp);
-
- if (pgd_none(pgd))
- return NULL;
-
- if (pgd_huge(pgd))
- return (pte_t *)pgdp;
-
- pudp = pud_offset(&pgd, addr);
- pud = READ_ONCE(*pudp);
- if (pud_none(pud))
- return NULL;
-
- if (pud_huge(pud))
- return (pte_t *)pudp;

- pmdp = pmd_offset(&pud, addr);
- pmd = READ_ONCE(*pmdp);
- if (pmd_none(pmd))
- return NULL;
-
- if (pmd_huge(pmd))
- return (pte_t *)pmdp;
- return NULL;
-}
-#endif /* !defined(CONFIG_PPC_64K_PAGES) || !defined(CONFIG_PPC_BOOK3S_64) */
-
-#if !defined(CONFIG_PPC_64K_PAGES) || !defined(CONFIG_PPC_BOOK3S_64)
static int __hugepte_alloc(struct mm_struct *mm, hugepd_t *hpdp,
unsigned long address, unsigned pdshift, unsigned pshift)
{
@@ -211,31 +176,6 @@ hugepd_search:

return hugepte_offset(*hpdp, addr, pdshift);
}
-
-#else
-pte_t *huge_pte_alloc(struct mm_struct *mm, unsigned long addr, unsigned long sz)
-{
- pgd_t *pg;
- pud_t *pu;
- pmd_t *pm;
- unsigned pshift = __ffs(sz);
-
- addr &= ~(sz-1);
- pg = pgd_offset(mm, addr);
-
- if (pshift == PGDIR_SHIFT) /* 16GB Huge Page */
- return (pte_t *)pg;
-
- pu = pud_alloc(mm, pg, addr); /* NA, skipped */
- if (pshift == PUD_SHIFT)
- return (pte_t *)pu;
-
- pm = pmd_alloc(mm, pu, addr); /* 16MB Huge Page */
- if (pshift == PMD_SHIFT)
- return (pte_t *)pm;
-
- return NULL;
-}
#endif
#else

Why these code need to be added on patch 4/9 but removed on 6/9?