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SubjectRe: [PATCH 2/4] mm: rmap: Allow platforms without mm_cpumask to defer TLB flush
Date
On Fri, Jul 8, 2022 at 8:28 PM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Fri, Jul 08, 2022 at 08:08:45AM +0000, Nadav Amit wrote:
>
> > Is it really only x86 that has mm_cpumask()?
>
> Unlikely, everybody who needs to IPI (eg. doesn't have broadcast
> invalidate) has benefit to track this mask more accurately.
>
> The below greps for clearing CPUs in the mask and ought to be a fair
> indicator:
>
> $ git grep -l "cpumask_clear_cpu.*mm_cpumask" arch/
> arch/arm/include/asm/mmu_context.h
> arch/loongarch/include/asm/mmu_context.h
> arch/loongarch/mm/tlb.c
> arch/mips/include/asm/mmu_context.h
> arch/openrisc/mm/tlb.c
> arch/powerpc/include/asm/book3s/64/mmu.h
> arch/powerpc/mm/book3s64/radix_tlb.c
> arch/riscv/mm/context.c
> arch/s390/kernel/smp.c
> arch/um/include/asm/mmu_context.h
> arch/x86/mm/tlb.c

so i suppose we need the below at this moment. i am not able to
test all of them. but since only x86 has already got tlbbatch
and arm64 is the second one to have tlbbatch now, i suppose the
below changes won't break those archs without tlbbatch. i would
expect people bringing up tlbbatch in those platforms to test
them later,

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;
Thanks
Barry

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