Activate the RCU fast_gup for ARM. We also need to force THP splits to
broadcast an IPI s.t. we block in the fast_gup page walker. As THP
splits are comparatively rare, this should not lead to a noticeable
performance degradation.
Signed-off-by: Steve Capper <steve.capper@xxxxxxxxxx>
---
arch/arm/Kconfig | 3 +++
arch/arm/include/asm/pgtable-3level.h | 6 ++++++
arch/arm/mm/flush.c | 19 +++++++++++++++++++
3 files changed, 28 insertions(+)
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 6cfdb3b..d0572f1 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -1803,6 +1803,9 @@ config ARCH_SELECT_MEMORY_MODEL
config HAVE_ARCH_PFN_VALID
def_bool ARCH_HAS_HOLES_MEMORYMODEL || !SPARSEMEM
+config HAVE_RCU_GUP
+ def_bool y
+
config HIGHMEM
bool "High Memory Support"
depends on MMU
diff --git a/arch/arm/include/asm/pgtable-3level.h b/arch/arm/include/asm/pgtable-3level.h
index b286ba9..fdc4a4f 100644
--- a/arch/arm/include/asm/pgtable-3level.h
+++ b/arch/arm/include/asm/pgtable-3level.h
@@ -226,6 +226,12 @@ static inline pte_t pte_mkspecial(pte_t 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)
+
+#ifdef CONFIG_HAVE_RCU_TABLE_FREE
+#define __HAVE_ARCH_PMDP_SPLITTING_FLUSH
+void pmdp_splitting_flush(struct vm_area_struct *vma, unsigned long address,
+ pmd_t *pmdp);
+#endif
#endif
#define PMD_BIT_FUNC(fn,op) \
diff --git a/arch/arm/mm/flush.c b/arch/arm/mm/flush.c
index 3387e60..91a2b59 100644
--- a/arch/arm/mm/flush.c
+++ b/arch/arm/mm/flush.c
@@ -377,3 +377,22 @@ void __flush_anon_page(struct vm_area_struct *vma, struct page *page, unsigned l
*/
__cpuc_flush_dcache_area(page_address(page), PAGE_SIZE);
}
+
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+#ifdef CONFIG_HAVE_RCU_TABLE_FREE
+static void thp_splitting_flush_sync(void *arg)
+{
+}
+
+void pmdp_splitting_flush(struct vm_area_struct *vma, unsigned long address,
+ pmd_t *pmdp)
+{
+ pmd_t pmd = pmd_mksplitting(*pmdp);
+ VM_BUG_ON(address & ~PMD_MASK);
+ set_pmd_at(vma->vm_mm, address, pmdp, pmd);
+
+ /* dummy IPI to serialise against fast_gup */
+ smp_call_function(thp_splitting_flush_sync, NULL, 1);
+}
+#endif /* CONFIG_HAVE_RCU_TABLE_FREE */
+#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
--
1.8.1.4
--
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