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

[Barry Song]

From: Barry Song <v-songbaohua@xxxxxxxx>

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 <v-songbaohua@xxxxxxxx>>
---
 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