[PATCH v2 2/4] mm: rmap: Allow platforms without mm_cpumask to defer TLB flush

From: Barry Song <hidden>
Date: 2022-07-11 03:47:02
Also in: linux-arm-kernel, linux-doc, linux-mips, linux-mm, linux-riscv, linux-s390, lkml
Subsystem: arm port, linux for powerpc (32-bit and 64-bit), loongarch, memory management, memory management - core, memory management - rmap (reverse mapping), mips, openrisc architecture, risc-v architecture, s390 architecture, the rest, user-mode linux (uml), x86 architecture (32-bit and 64-bit) · Maintainers: Russell King, Madhavan Srinivasan, Huacai Chen, Andrew Morton, David Hildenbrand, Lorenzo Stoakes, Thomas Bogendoerfer, Jonas Bonn, Stefan Kristiansson, Stafford Horne, Paul Walmsley, Palmer Dabbelt, Albert Ou, Heiko Carstens, Vasily Gorbik, Alexander Gordeev, Linus Torvalds, Richard Weinberger, Anton Ivanov, Johannes Berg, Thomas Gleixner, Ingo Molnar, Borislav Petkov, Dave Hansen

From: Barry Song <redacted>

Platforms like ARM64 have hareware TLB shootdown broadcast. They
don't maintain mm_cpumask but just send tlbi and related sync
instructions for TLB flush. task's mm_cpumask is normally empty
in this case. We also allow deferred TLB flush on this kind of
platforms.

Signed-off-by: Barry Song <redacted>>
---
 arch/arm/Kconfig       | 1 +
 arch/loongarch/Kconfig | 1 +
 arch/mips/Kconfig      | 1 +
 arch/openrisc/Kconfig  | 1 +
 arch/powerpc/Kconfig   | 1 +
 arch/riscv/Kconfig     | 1 +
 arch/s390/Kconfig      | 1 +
 arch/um/Kconfig        | 1 +
 arch/x86/Kconfig       | 1 +
 mm/Kconfig             | 3 +++
 mm/rmap.c              | 4 ++++
 11 files changed, 16 insertions(+)

diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index 7630ba9cb6cc..25c42747f488 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig

@@ -13,6 +13,7 @@ config ARM
 	select ARCH_HAS_KEEPINITRD
 	select ARCH_HAS_KCOV
 	select ARCH_HAS_MEMBARRIER_SYNC_CORE
+	select ARCH_HAS_MM_CPUMASK
 	select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
 	select ARCH_HAS_PTE_SPECIAL if ARM_LPAE
 	select ARCH_HAS_PHYS_TO_DMA

diff --git a/arch/loongarch/Kconfig b/arch/loongarch/Kconfig
index 1920d52653b4..4b737c0d17a2 100644
--- a/arch/loongarch/Kconfig
+++ b/arch/loongarch/Kconfig

@@ -7,6 +7,7 @@ config LOONGARCH
 	select ARCH_ENABLE_MEMORY_HOTPLUG
 	select ARCH_ENABLE_MEMORY_HOTREMOVE
 	select ARCH_HAS_ACPI_TABLE_UPGRADE	if ACPI
+	select ARCH_HAS_MM_CPUMASK
 	select ARCH_HAS_PHYS_TO_DMA
 	select ARCH_HAS_PTE_SPECIAL
 	select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST

diff --git a/arch/mips/Kconfig b/arch/mips/Kconfig
index db09d45d59ec..1b196acdeca3 100644
--- a/arch/mips/Kconfig
+++ b/arch/mips/Kconfig

@@ -9,6 +9,7 @@ config MIPS
 	select ARCH_HAS_FORTIFY_SOURCE
 	select ARCH_HAS_KCOV
 	select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE if !EVA
+	select ARCH_HAS_MM_CPUMASK
 	select ARCH_HAS_PTE_SPECIAL if !(32BIT && CPU_HAS_RIXI)
 	select ARCH_HAS_STRNCPY_FROM_USER
 	select ARCH_HAS_STRNLEN_USER

diff --git a/arch/openrisc/Kconfig b/arch/openrisc/Kconfig
index e814df4c483c..82483b192f4a 100644
--- a/arch/openrisc/Kconfig
+++ b/arch/openrisc/Kconfig

@@ -9,6 +9,7 @@ config OPENRISC
 	select ARCH_32BIT_OFF_T
 	select ARCH_HAS_DMA_SET_UNCACHED
 	select ARCH_HAS_DMA_CLEAR_UNCACHED
+	select ARCH_HAS_MM_CPUMASK
 	select ARCH_HAS_SYNC_DMA_FOR_DEVICE
 	select COMMON_CLK
 	select OF

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index c2ce2e60c8f0..19061ffe73a0 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig

@@ -127,6 +127,7 @@ config PPC
 	select ARCH_HAS_MEMBARRIER_SYNC_CORE
 	select ARCH_HAS_MEMREMAP_COMPAT_ALIGN	if PPC_64S_HASH_MMU
 	select ARCH_HAS_MMIOWB			if PPC64
+	select ARCH_HAS_MM_CPUMASK
 	select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
 	select ARCH_HAS_PHYS_TO_DMA
 	select ARCH_HAS_PMEM_API

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index c22f58155948..7570c95a9cc8 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig

@@ -25,6 +25,7 @@ config RISCV
 	select ARCH_HAS_GIGANTIC_PAGE
 	select ARCH_HAS_KCOV
 	select ARCH_HAS_MMIOWB
+	select ARCH_HAS_MM_CPUMASK
 	select ARCH_HAS_PTE_SPECIAL
 	select ARCH_HAS_SET_DIRECT_MAP if MMU
 	select ARCH_HAS_SET_MEMORY if MMU

diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index 91c0b80a8bf0..48d91fa05bab 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig

@@ -73,6 +73,7 @@ config S390
 	select ARCH_HAS_GIGANTIC_PAGE
 	select ARCH_HAS_KCOV
 	select ARCH_HAS_MEM_ENCRYPT
+	select ARCH_HAS_MM_CPUMASK
 	select ARCH_HAS_PTE_SPECIAL
 	select ARCH_HAS_SCALED_CPUTIME
 	select ARCH_HAS_SET_MEMORY

diff --git a/arch/um/Kconfig b/arch/um/Kconfig
index 4ec22e156a2e..df29c729267b 100644
--- a/arch/um/Kconfig
+++ b/arch/um/Kconfig

@@ -8,6 +8,7 @@ config UML
 	select ARCH_EPHEMERAL_INODES
 	select ARCH_HAS_GCOV_PROFILE_ALL
 	select ARCH_HAS_KCOV
+	select ARCH_HAS_MM_CPUMASK
 	select ARCH_HAS_STRNCPY_FROM_USER
 	select ARCH_HAS_STRNLEN_USER
 	select ARCH_NO_PREEMPT

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index be0b95e51df6..a91d73866238 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig

@@ -81,6 +81,7 @@ config X86
 	select ARCH_HAS_KCOV			if X86_64
 	select ARCH_HAS_MEM_ENCRYPT
 	select ARCH_HAS_MEMBARRIER_SYNC_CORE
+	select ARCH_HAS_MM_CPUMASK
 	select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE
 	select ARCH_HAS_PMEM_API		if X86_64
 	select ARCH_HAS_PTE_DEVMAP		if X86_64

diff --git a/mm/Kconfig b/mm/Kconfig
index 169e64192e48..7bf54f57ca01 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig

@@ -951,6 +951,9 @@ config ARCH_HAS_CURRENT_STACK_POINTER
 	  register alias named "current_stack_pointer", this config can be
 	  selected.
 
+config ARCH_HAS_MM_CPUMASK
+	bool
+
 config ARCH_HAS_VM_GET_PAGE_PROT
 	bool

diff --git a/mm/rmap.c b/mm/rmap.c
index 5bcb334cd6f2..13d4f9a1d4f1 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c

@@ -692,6 +692,10 @@ static bool should_defer_flush(struct mm_struct *mm, enum ttu_flags flags)
 	if (!(flags & TTU_BATCH_FLUSH))
 		return false;
 
+#ifndef CONFIG_ARCH_HAS_MM_CPUMASK
+	return true;
+#endif
+
 	/* If remote CPUs need to be flushed then defer batch the flush */
 	if (cpumask_any_but(mm_cpumask(mm), get_cpu()) < nr_cpu_ids)
 		should_defer = true;

-- 
2.25.1

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