linux-kernel - [PATCH 01/19] mm: Introduce ARCH_SUPPORTS_HUGE

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Message-ID: <20240809160909.1023470-2-peterx@redhat.com>
Date: Fri,  9 Aug 2024 12:08:51 -0400
From: Peter Xu <peterx@...hat.com>
To: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Cc: Sean Christopherson <seanjc@...gle.com>,
	Oscar Salvador <osalvador@...e.de>,
	Jason Gunthorpe <jgg@...dia.com>,
	Axel Rasmussen <axelrasmussen@...gle.com>,
	linux-arm-kernel@...ts.infradead.org,
	x86@...nel.org,
	peterx@...hat.com,
	Will Deacon <will@...nel.org>,
	Gavin Shan <gshan@...hat.com>,
	Paolo Bonzini <pbonzini@...hat.com>,
	Zi Yan <ziy@...dia.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Catalin Marinas <catalin.marinas@....com>,
	Ingo Molnar <mingo@...hat.com>,
	Alistair Popple <apopple@...dia.com>,
	Borislav Petkov <bp@...en8.de>,
	David Hildenbrand <david@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	kvm@...r.kernel.org,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Alex Williamson <alex.williamson@...hat.com>,
	Yan Zhao <yan.y.zhao@...el.com>
Subject: [PATCH 01/19] mm: Introduce ARCH_SUPPORTS_HUGE_PFNMAP and special bits to pmd/pud

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@...hat.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