[PATCH 01/19] mm: Introduce ARCH_SUPPORTS_HUGE_PFNMAP and special bits to pmd/pud

Peter Xu
2024-08-09T16:09:23Z

This patch introduces the option to introduce special pte bit into
pmd/puds. Archs can start to define pmd_special / pud_special when
supported by selecting the new option. Per-arch support will be added
later.

Before that, create fallbacks for these helpers so that they are always
available.

Signed-off-by: Peter Xu <peterx@redhat.com>
---
include/linux/mm.h | 24 ++++++++++++++++++++++++
mm/Kconfig | 13 +++++++++++++
2 files changed, 37 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 43b40334e9b2..90ca84200800 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2644,6 +2644,30 @@ static inline pte_t pte_mkspecial(pte_t pte)
}
#endif

+#ifndef CONFIG_ARCH_SUPPORTS_PMD_PFNMAP
+static inline bool pmd_special(pmd_t pmd)
+{
+ return false;
+}
+
+static inline pmd_t pmd_mkspecial(pmd_t pmd)
+{
+ return pmd;
+}
+#endif /* CONFIG_ARCH_SUPPORTS_PMD_PFNMAP */
+
+#ifndef CONFIG_ARCH_SUPPORTS_PUD_PFNMAP
+static inline bool pud_special(pud_t pud)
+{
+ return false;
+}
+
+static inline pud_t pud_mkspecial(pud_t pud)
+{
+ return pud;
+}
+#endif /* CONFIG_ARCH_SUPPORTS_PUD_PFNMAP */
+
#ifndef CONFIG_ARCH_HAS_PTE_DEVMAP
static inline int pte_devmap(pte_t pte)
{
diff --git a/mm/Kconfig b/mm/Kconfig
index 3936fe4d26d9..3db0eebb53e2 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -881,6 +881,19 @@ endif # TRANSPARENT_HUGEPAGE
config PGTABLE_HAS_HUGE_LEAVES
def_bool TRANSPARENT_HUGEPAGE || HUGETLB_PAGE

+# TODO: Allow to be enabled without THP
+config ARCH_SUPPORTS_HUGE_PFNMAP
+ def_bool n
+ depends on TRANSPARENT_HUGEPAGE
+
+config ARCH_SUPPORTS_PMD_PFNMAP
+ def_bool y
+ depends on ARCH_SUPPORTS_HUGE_PFNMAP && HAVE_ARCH_TRANSPARENT_HUGEPAGE
+
+config ARCH_SUPPORTS_PUD_PFNMAP
+ def_bool y
+ depends on ARCH_SUPPORTS_HUGE_PFNMAP && HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
+
#
# UP and nommu archs use km based percpu allocator
#
--
2.45.0