linux-kernel - [PATCH 5/6] powerpc/64s: Do not disable preemption in lazy MMU mode

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Message-ID: <448f6e26a9d72fb2c873245ea948807491f6b798.1749747752.git.agordeev@linux.ibm.com>
Date: Thu, 12 Jun 2025 19:36:12 +0200
From: Alexander Gordeev <agordeev@...ux.ibm.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        sparclinux@...r.kernel.org, xen-devel@...ts.xenproject.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        Hugh Dickins <hughd@...gle.com>, Nicholas Piggin <npiggin@...il.com>,
        Guenter Roeck <linux@...ck-us.net>, Juergen Gross <jgross@...e.com>,
        Jeremy Fitzhardinge <jeremy@...p.org>,
        Ryan Roberts <ryan.roberts@....com>
Subject: [PATCH 5/6] powerpc/64s: Do not disable preemption in lazy MMU mode

Commit b9ef323ea168 ("powerpc/64s: Disable preemption in hash lazy
mmu mode") is not necessary anymore, since the lazy MMU mode is
entered with a spinlock held and powerpc does not support Real-Time.
Thus, upon entering the lazy mode the preemption is already disabled.

Signed-off-by: Alexander Gordeev <agordeev@...ux.ibm.com>
---
 arch/powerpc/include/asm/book3s/64/tlbflush-hash.h | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h b/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h
index 146287d9580f..aeac22b576c8 100644
--- a/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h
+++ b/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h
@@ -30,13 +30,9 @@ static inline void arch_enter_lazy_mmu_mode(void)
 {
 	struct ppc64_tlb_batch *batch;
 
+	VM_WARN_ON_ONCE(preemptible());
 	if (radix_enabled())
 		return;
-	/*
-	 * apply_to_page_range can call us this preempt enabled when
-	 * operating on kernel page tables.
-	 */
-	preempt_disable();
 	batch = this_cpu_ptr(&ppc64_tlb_batch);
 	batch->active = 1;
 }
@@ -45,6 +41,7 @@ static inline void arch_leave_lazy_mmu_mode(void)
 {
 	struct ppc64_tlb_batch *batch;
 
+	VM_WARN_ON_ONCE(preemptible());
 	if (radix_enabled())
 		return;
 	batch = this_cpu_ptr(&ppc64_tlb_batch);
@@ -52,10 +49,12 @@ static inline void arch_leave_lazy_mmu_mode(void)
 	if (batch->index)
 		__flush_tlb_pending(batch);
 	batch->active = 0;
-	preempt_enable();
 }
 
-#define arch_flush_lazy_mmu_mode()      do {} while (0)
+static inline void arch_flush_lazy_mmu_mode(void)
+{
+	VM_WARN_ON_ONCE(preemptible());
+}
 
 extern void hash__tlbiel_all(unsigned int action);
 
-- 
2.48.1