diff mbox

[2/3] arm64: mm: Route pmd thp functions through pte equivalents

Message ID 1391696171-8922-3-git-send-email-steve.capper@linaro.org (mailing list archive)
State New, archived
Headers show

Commit Message

Steve Capper Feb. 6, 2014, 2:16 p.m. UTC 
Rather than have separate hugetlb and transparent huge page pmd
manipulation functions, re-wire our thp functions to simply call the
pte equivalents.

This allows THP to take advantage of the new PTE_WRITE logic introduced
in:
  c2c93e5 arm64: mm: Introduce PTE_WRITE

To represent splitting THPs we use the PTE_SPECIAL bit as this is not
used for pmds.

Signed-off-by: Steve Capper <steve.capper@linaro.org>
---
 arch/arm64/include/asm/pgtable.h | 67 +++++++++++++++++++++-------------------
 1 file changed, 35 insertions(+), 32 deletions(-)

Comments

Catalin Marinas Feb. 12, 2014, 10:14 a.m. UTC | #1 
On Thu, Feb 06, 2014 at 02:16:10PM +0000, Steve Capper wrote:
> Rather than have separate hugetlb and transparent huge page pmd
> manipulation functions, re-wire our thp functions to simply call the
> pte equivalents.

That's one thing I don't like about hugetlb, casting pmds to ptes. Do we
actually save much in terms of code clean-up by doing this?
Steve Capper Feb. 12, 2014, 10:32 a.m. UTC | #2 
On Wed, Feb 12, 2014 at 10:14:23AM +0000, Catalin Marinas wrote:
> On Thu, Feb 06, 2014 at 02:16:10PM +0000, Steve Capper wrote:
> > Rather than have separate hugetlb and transparent huge page pmd
> > manipulation functions, re-wire our thp functions to simply call the
> > pte equivalents.
> 
> That's one thing I don't like about hugetlb, casting pmds to ptes. Do we
> actually save much in terms of code clean-up by doing this?

Hi Catalin,

At the moment we have ptes and hugetlb ptes behaving in the same way so
they both make use of PTE_WRITE. I thought it would be more logical to
tie the THP code to the pte manipulation functions too rather than
duplicate the PTE_WRITE logic in a separate PMD_WRITE. This makes
future pte changes apply to THP too automatically (along with hugetlb).

Cheers,
Catalin Marinas Feb. 20, 2014, 5 p.m. UTC | #3 
On Wed, Feb 12, 2014 at 10:32:38AM +0000, Steve Capper wrote:
> On Wed, Feb 12, 2014 at 10:14:23AM +0000, Catalin Marinas wrote:
> > On Thu, Feb 06, 2014 at 02:16:10PM +0000, Steve Capper wrote:
> > > Rather than have separate hugetlb and transparent huge page pmd
> > > manipulation functions, re-wire our thp functions to simply call the
> > > pte equivalents.
> > 
> > That's one thing I don't like about hugetlb, casting pmds to ptes. Do we
> > actually save much in terms of code clean-up by doing this?
> 
> At the moment we have ptes and hugetlb ptes behaving in the same way so
> they both make use of PTE_WRITE. I thought it would be more logical to
> tie the THP code to the pte manipulation functions too rather than
> duplicate the PTE_WRITE logic in a separate PMD_WRITE. This makes
> future pte changes apply to THP too automatically (along with hugetlb).

OK, let's go with this, it's difficult to change hugetlb the other way.

BTW, powerpc and tile heavily simplify this using macros and
pte_pmd/pmd_pte macros.
diff mbox

Patch

diff --git a/arch/arm64/include/asm/pgtable.h b/arch/arm64/include/asm/pgtable.h
index a3fb1e4..a5d5832 100644
--- a/arch/arm64/include/asm/pgtable.h
+++ b/arch/arm64/include/asm/pgtable.h
@@ -228,59 +228,65 @@  static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
 #define __HAVE_ARCH_PTE_SPECIAL
 
 /*
- * Software PMD bits for THP
- */
-
-#define PMD_SECT_DIRTY		(_AT(pmdval_t, 1) << 55)
-#define PMD_SECT_SPLITTING	(_AT(pmdval_t, 1) << 57)
-
-/*
  * THP definitions.
  */
-#define pmd_young(pmd)		(pmd_val(pmd) & PMD_SECT_AF)
-
 #define __HAVE_ARCH_PMD_WRITE
-#define pmd_write(pmd)		(!(pmd_val(pmd) & PMD_SECT_RDONLY))
+static inline long pmd_write(pmd_t pmd)
+{
+	pte_t pte = __pte(pmd_val(pmd));
+	return pte_write(pte);
+}
 
 #ifdef CONFIG_TRANSPARENT_HUGEPAGE
 #define pmd_trans_huge(pmd)	(pmd_val(pmd) && !(pmd_val(pmd) & PMD_TABLE_BIT))
-#define pmd_trans_splitting(pmd) (pmd_val(pmd) & PMD_SECT_SPLITTING)
+
+static inline long pmd_trans_splitting(pmd_t pmd)
+{
+	pte_t pte = __pte(pmd_val(pmd));
+	return pte_special(pte);
+}
 #endif
 
+static inline long pmd_young(pmd_t pmd)
+{
+	pte_t pte = __pte(pmd_val(pmd));
+	return pte_young(pte);
+}
+
 static inline pmd_t pmd_wrprotect(pmd_t pmd)
 {
-	pmd_val(pmd) |= PMD_SECT_RDONLY;
-	return pmd;
+	pte_t pte = pte_wrprotect(__pte(pmd_val(pmd)));
+	return __pmd(pte_val(pte));
 }
 
 static inline pmd_t pmd_mkold(pmd_t pmd)
 {
-	pmd_val(pmd) &= ~PMD_SECT_AF;
-	return pmd;
+	pte_t pte = pte_mkold(__pte(pmd_val(pmd)));
+	return __pmd(pte_val(pte));
 }
 
 static inline pmd_t pmd_mksplitting(pmd_t pmd)
 {
-	pmd_val(pmd) |= PMD_SECT_SPLITTING;
-	return pmd;
+	pte_t pte = pte_mkspecial(__pte(pmd_val(pmd)));
+	return __pmd(pte_val(pte));
 }
 
 static inline pmd_t pmd_mkwrite(pmd_t pmd)
 {
-	pmd_val(pmd) &= ~PMD_SECT_RDONLY;
-	return pmd;
+	pte_t pte = pte_mkwrite(__pte(pmd_val(pmd)));
+	return __pmd(pte_val(pte));
 }
 
 static inline pmd_t pmd_mkdirty(pmd_t pmd)
 {
-	pmd_val(pmd) |= PMD_SECT_DIRTY;
-	return pmd;
+	pte_t pte = pte_mkdirty(__pte(pmd_val(pmd)));
+	return __pmd(pte_val(pte));
 }
 
 static inline pmd_t pmd_mkyoung(pmd_t pmd)
 {
-	pmd_val(pmd) |= PMD_SECT_AF;
-	return pmd;
+	pte_t pte = pte_mkyoung(__pte(pmd_val(pmd)));
+	return __pmd(pte_val(pte));
 }
 
 static inline pmd_t pmd_mknotpresent(pmd_t pmd)
@@ -297,15 +303,6 @@  static inline pmd_t pmd_mknotpresent(pmd_t pmd)
 
 #define pmd_page(pmd)           pfn_to_page(__phys_to_pfn(pmd_val(pmd) & PHYS_MASK))
 
-static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
-{
-	const pmdval_t mask = PMD_SECT_USER | PMD_SECT_PXN | PMD_SECT_UXN |
-			      PMD_SECT_RDONLY | PMD_SECT_PROT_NONE |
-			      PMD_SECT_VALID;
-	pmd_val(pmd) = (pmd_val(pmd) & ~mask) | (pgprot_val(newprot) & mask);
-	return pmd;
-}
-
 #define set_pmd_at(mm, addr, pmdp, pmd)	set_pmd(pmdp, pmd)
 
 static inline int has_transparent_hugepage(void)
@@ -414,6 +411,12 @@  static inline pte_t pte_modify(pte_t pte, pgprot_t newprot)
 	return pte;
 }
 
+static inline pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot)
+{
+	pte_t pte = pte_modify(__pte(pmd_val(pmd)), newprot);
+	return __pmd(pte_val(pte));
+}
+
 extern pgd_t swapper_pg_dir[PTRS_PER_PGD];
 extern pgd_t idmap_pg_dir[PTRS_PER_PGD];