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mm: bail out of lazy_mmu_mode_* in interrupt context

The lazy MMU mode cannot be used in interrupt context. This is documented
in <linux/pgtable.h>, but isn't consistently handled across architectures.

arm64 ensures that calls to lazy_mmu_mode_* have no effect in interrupt
context, because such calls do occur in certain configurations - see
commit b81c688426a9 ("arm64/mm: Disable barrier batching in interrupt
contexts"). Other architectures do not check this situation, most likely
because it hasn't occurred so far.

Let's handle this in the new generic lazy_mmu layer, in the same fashion
as arm64: bail out of lazy_mmu_mode_* if in_interrupt(). Also remove the
arm64 handling that is now redundant.

Both arm64 and x86/Xen also ensure that any lazy MMU optimisation is
disabled while in interrupt (see queue_pte_barriers() and
xen_get_lazy_mode() respectively). This will be handled in the generic
layer in a subsequent patch.

Link: https://lkml.kernel.org/r/20251215150323.2218608-9-kevin.brodsky@arm.com
Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
Acked-by: David Hildenbrand (Red Hat) <david@kernel.org>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Andreas Larsson <andreas@gaisler.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 <david@redhat.com>
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: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
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>

authored by

Kevin Brodsky and committed by
Andrew Morton
9273dfae 0a096ab7

+16 -10
-9
arch/arm64/include/asm/pgtable.h
··· 94 94 * keeps tracking simple. 95 95 */ 96 96 97 - if (in_interrupt()) 98 - return; 99 - 100 97 set_thread_flag(TIF_LAZY_MMU); 101 98 } 102 99 103 100 static inline void arch_flush_lazy_mmu_mode(void) 104 101 { 105 - if (in_interrupt()) 106 - return; 107 - 108 102 if (test_and_clear_thread_flag(TIF_LAZY_MMU_PENDING)) 109 103 emit_pte_barriers(); 110 104 } 111 105 112 106 static inline void arch_leave_lazy_mmu_mode(void) 113 107 { 114 - if (in_interrupt()) 115 - return; 116 - 117 108 arch_flush_lazy_mmu_mode(); 118 109 clear_thread_flag(TIF_LAZY_MMU); 119 110 }
+16 -1
include/linux/pgtable.h
··· 233 233 * preemption, as a consequence generic code may not sleep while the lazy MMU 234 234 * mode is active. 235 235 * 236 - * Nesting is not permitted and the mode cannot be used in interrupt context. 236 + * The mode is disabled in interrupt context and calls to the lazy_mmu API have 237 + * no effect. 238 + * 239 + * Nesting is not permitted. 237 240 */ 238 241 #ifdef CONFIG_ARCH_HAS_LAZY_MMU_MODE 239 242 static inline void lazy_mmu_mode_enable(void) 240 243 { 244 + if (in_interrupt()) 245 + return; 246 + 241 247 arch_enter_lazy_mmu_mode(); 242 248 } 243 249 244 250 static inline void lazy_mmu_mode_disable(void) 245 251 { 252 + if (in_interrupt()) 253 + return; 254 + 246 255 arch_leave_lazy_mmu_mode(); 247 256 } 248 257 249 258 static inline void lazy_mmu_mode_pause(void) 250 259 { 260 + if (in_interrupt()) 261 + return; 262 + 251 263 arch_leave_lazy_mmu_mode(); 252 264 } 253 265 254 266 static inline void lazy_mmu_mode_resume(void) 255 267 { 268 + if (in_interrupt()) 269 + return; 270 + 256 271 arch_enter_lazy_mmu_mode(); 257 272 } 258 273 #else