mm: introduce CONFIG_ARCH_HAS_LAZY_MMU_MODE

Architectures currently opt in for implementing lazy_mmu helpers by
defining __HAVE_ARCH_ENTER_LAZY_MMU_MODE.

In preparation for introducing a generic lazy_mmu layer that will require
storage in task_struct, let's switch to a cleaner approach: instead of
defining a macro, select a CONFIG option.

This patch introduces CONFIG_ARCH_HAS_LAZY_MMU_MODE and has each arch
select it when it implements lazy_mmu helpers. 
__HAVE_ARCH_ENTER_LAZY_MMU_MODE is removed and <linux/pgtable.h> relies on
the new CONFIG instead.

On x86, lazy_mmu helpers are only implemented if PARAVIRT_XXL is selected.
This creates some complications in arch/x86/boot/, because a few files
manually undefine PARAVIRT* options.  As a result <asm/paravirt.h> does
not define the lazy_mmu helpers, but this breaks the build as
<linux/pgtable.h> only defines them if !CONFIG_ARCH_HAS_LAZY_MMU_MODE. 
There does not seem to be a clean way out of this - let's just undefine
that new CONFIG too.

Link: https://lkml.kernel.org/r/20251215150323.2218608-7-kevin.brodsky@arm.com
Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Acked-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Reviewed-by: Ryan Roberts <ryan.roberts@arm.com>
Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
Acked-by: Andreas Larsson <andreas@gaisler.com>	[sparc]
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: David Hildenbrand (Red Hat) <david@kernel.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jann Horn <jannh@google.com>
Cc: Juegren Gross <jgross@suse.com>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Cc: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

arch/arm64/Kconfig

@@ -35,6 +35,7 @@ config ARM64
 	select ARCH_HAS_KCOV
 	select ARCH_HAS_KERNEL_FPU_SUPPORT if KERNEL_MODE_NEON
 	select ARCH_HAS_KEEPINITRD
+	select ARCH_HAS_LAZY_MMU_MODE
 	select ARCH_HAS_MEMBARRIER_SYNC_CORE
 	select ARCH_HAS_MEM_ENCRYPT
 	select ARCH_SUPPORTS_MSEAL_SYSTEM_MAPPINGS

arch/arm64/include/asm/pgtable.h

@@ -80,7 +80,6 @@ static inline void queue_pte_barriers(void)
 	}
 }
 
-#define  __HAVE_ARCH_ENTER_LAZY_MMU_MODE
 static inline void arch_enter_lazy_mmu_mode(void)
 {
 	/*

arch/powerpc/include/asm/book3s/64/tlbflush-hash.h

@@ -24,8 +24,6 @@ DECLARE_PER_CPU(struct ppc64_tlb_batch, ppc64_tlb_batch);
 
 extern void __flush_tlb_pending(struct ppc64_tlb_batch *batch);
 
-#define __HAVE_ARCH_ENTER_LAZY_MMU_MODE
-
 static inline void arch_enter_lazy_mmu_mode(void)
 {
 	struct ppc64_tlb_batch *batch;

arch/powerpc/platforms/Kconfig.cputype

@@ -93,6 +93,7 @@ config PPC_BOOK3S_64
 	select IRQ_WORK
 	select PPC_64S_HASH_MMU if !PPC_RADIX_MMU
 	select KASAN_VMALLOC if KASAN
+	select ARCH_HAS_LAZY_MMU_MODE
 
 config PPC_BOOK3E_64
 	bool "Embedded processors"

arch/sparc/Kconfig

@@ -112,6 +112,7 @@ config SPARC64
 	select NEED_PER_CPU_PAGE_FIRST_CHUNK
 	select ARCH_SUPPORTS_SCHED_SMT if SMP
 	select ARCH_SUPPORTS_SCHED_MC  if SMP
+	select ARCH_HAS_LAZY_MMU_MODE
 
 config ARCH_PROC_KCORE_TEXT
 	def_bool y

arch/sparc/include/asm/tlbflush_64.h

@@ -39,8 +39,6 @@ static inline void flush_tlb_range(struct vm_area_struct *vma,
 
 void flush_tlb_kernel_range(unsigned long start, unsigned long end);
 
-#define __HAVE_ARCH_ENTER_LAZY_MMU_MODE
-
 void flush_tlb_pending(void);
 void arch_enter_lazy_mmu_mode(void);
 void arch_flush_lazy_mmu_mode(void);

arch/x86/Kconfig

@@ -808,6 +808,7 @@ config PARAVIRT
 config PARAVIRT_XXL
 	bool
 	depends on X86_64
+	select ARCH_HAS_LAZY_MMU_MODE
 
 config PARAVIRT_DEBUG
 	bool "paravirt-ops debugging"

arch/x86/boot/compressed/misc.h

@@ -11,6 +11,7 @@
 #undef CONFIG_PARAVIRT
 #undef CONFIG_PARAVIRT_XXL
 #undef CONFIG_PARAVIRT_SPINLOCKS
+#undef CONFIG_ARCH_HAS_LAZY_MMU_MODE
 #undef CONFIG_KASAN
 #undef CONFIG_KASAN_GENERIC
 

arch/x86/boot/startup/sme.c

@@ -24,6 +24,7 @@
 #undef CONFIG_PARAVIRT
 #undef CONFIG_PARAVIRT_XXL
 #undef CONFIG_PARAVIRT_SPINLOCKS
+#undef CONFIG_ARCH_HAS_LAZY_MMU_MODE
 
 /*
  * This code runs before CPU feature bits are set. By default, the

arch/x86/include/asm/paravirt.h

@@ -526,7 +526,6 @@ static inline void arch_end_context_switch(struct task_struct *next)
 	PVOP_VCALL1(cpu.end_context_switch, next);
 }
 
-#define  __HAVE_ARCH_ENTER_LAZY_MMU_MODE
 static inline void arch_enter_lazy_mmu_mode(void)
 {
 	PVOP_VCALL0(mmu.lazy_mode.enter);

include/linux/pgtable.h

@@ -235,7 +235,7 @@ static inline int pmd_dirty(pmd_t pmd)
  *
  * Nesting is not permitted and the mode cannot be used in interrupt context.
  */
-#ifndef __HAVE_ARCH_ENTER_LAZY_MMU_MODE
+#ifndef CONFIG_ARCH_HAS_LAZY_MMU_MODE
 static inline void arch_enter_lazy_mmu_mode(void) {}
 static inline void arch_leave_lazy_mmu_mode(void) {}
 static inline void arch_flush_lazy_mmu_mode(void) {}

mm/Kconfig

@@ -1468,6 +1468,13 @@ config PT_RECLAIM
 config FIND_NORMAL_PAGE
 	def_bool n
 
+config ARCH_HAS_LAZY_MMU_MODE
+	bool
+	help
+	  The architecture uses the lazy MMU mode. This allows changes to
+	  MMU-related architectural state to be deferred until the mode is
+	  exited. See <linux/pgtable.h> for details.
+
 source "mm/damon/Kconfig"
 
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