linux-kernel - [PATCH 6/6] powerpc/64s: Do not re-activate batched TLB flush

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Message-ID: <8625a1d97dcf4ae499b4bb341e27346f768a7248.1749747752.git.agordeev@linux.ibm.com>
Date: Thu, 12 Jun 2025 19:36:13 +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 6/6] powerpc/64s: Do not re-activate batched TLB flush

Since commit b9ef323ea168 ("powerpc/64s: Disable preemption in hash
lazy mmu mode") a task can not be preempted while in lazy MMU mode.
Therefore, the batch re-activation code is never called, so remove it.

Signed-off-by: Alexander Gordeev <agordeev@...ux.ibm.com>
---
 arch/powerpc/include/asm/thread_info.h |  2 --
 arch/powerpc/kernel/process.c          | 25 -------------------------
 2 files changed, 27 deletions(-)

diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h
index 2785c7462ebf..092118a68862 100644
--- a/arch/powerpc/include/asm/thread_info.h
+++ b/arch/powerpc/include/asm/thread_info.h
@@ -154,12 +154,10 @@ void arch_setup_new_exec(void);
 /* Don't move TLF_NAPPING without adjusting the code in entry_32.S */
 #define TLF_NAPPING		0	/* idle thread enabled NAP mode */
 #define TLF_SLEEPING		1	/* suspend code enabled SLEEP mode */
-#define TLF_LAZY_MMU		3	/* tlb_batch is active */
 #define TLF_RUNLATCH		4	/* Is the runlatch enabled? */
 
 #define _TLF_NAPPING		(1 << TLF_NAPPING)
 #define _TLF_SLEEPING		(1 << TLF_SLEEPING)
-#define _TLF_LAZY_MMU		(1 << TLF_LAZY_MMU)
 #define _TLF_RUNLATCH		(1 << TLF_RUNLATCH)
 
 #ifndef __ASSEMBLY__
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 855e09886503..edb59a447149 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -1281,9 +1281,6 @@ struct task_struct *__switch_to(struct task_struct *prev,
 {
 	struct thread_struct *new_thread, *old_thread;
 	struct task_struct *last;
-#ifdef CONFIG_PPC_64S_HASH_MMU
-	struct ppc64_tlb_batch *batch;
-#endif
 
 	new_thread = &new->thread;
 	old_thread = &current->thread;
@@ -1291,14 +1288,6 @@ struct task_struct *__switch_to(struct task_struct *prev,
 	WARN_ON(!irqs_disabled());
 
 #ifdef CONFIG_PPC_64S_HASH_MMU
-	batch = this_cpu_ptr(&ppc64_tlb_batch);
-	if (batch->active) {
-		current_thread_info()->local_flags |= _TLF_LAZY_MMU;
-		if (batch->index)
-			__flush_tlb_pending(batch);
-		batch->active = 0;
-	}
-
 	/*
 	 * On POWER9 the copy-paste buffer can only paste into
 	 * foreign real addresses, so unprivileged processes can not
@@ -1369,20 +1358,6 @@ struct task_struct *__switch_to(struct task_struct *prev,
 	 */
 
 #ifdef CONFIG_PPC_BOOK3S_64
-#ifdef CONFIG_PPC_64S_HASH_MMU
-	/*
-	 * This applies to a process that was context switched while inside
-	 * arch_enter_lazy_mmu_mode(), to re-activate the batch that was
-	 * deactivated above, before _switch(). This will never be the case
-	 * for new tasks.
-	 */
-	if (current_thread_info()->local_flags & _TLF_LAZY_MMU) {
-		current_thread_info()->local_flags &= ~_TLF_LAZY_MMU;
-		batch = this_cpu_ptr(&ppc64_tlb_batch);
-		batch->active = 1;
-	}
-#endif
-
 	/*
 	 * Math facilities are masked out of the child MSR in copy_thread.
 	 * A new task does not need to restore_math because it will
-- 
2.48.1