Re: [PATCH v4 01/12] powerpc/64s: Do not re-activate batched TLB flush
From: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Date: 2025-11-05 02:55:17
Also in:
linux-arm-kernel, linux-mm, lkml, sparclinux, xen-devel
Kevin Brodsky [off-list ref] writes:
From: Alexander Gordeev <agordeev@linux.ibm.com>
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@linux.ibm.com>
Signed-off-by: Kevin Brodsky <redacted>
---
arch/powerpc/include/asm/thread_info.h | 2 --
arch/powerpc/kernel/process.c | 25 -------------------------
2 files changed, 27 deletions(-)Since the commit referenced in above disables the preemption in arch_enter_lazy_mmu(), so the expectation is that we will never be context switched while in lazy_mmu, hence the code changes in switch_to() around __flush_tlb_pending() should ideally never be called. With this analysis - the patch looks good to me. I will give this entire patch series a try on Power HW with Hash mmu too (which uses lazy mmu and let you know the results of that)! For this patch please feel free to add: Reviewed-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com> CC: Venkat who also runs CI on linux Power HW for upstream testing :) -ritesh
quoted hunk ↗ jump to hunk
diff --git a/arch/powerpc/include/asm/thread_info.h b/arch/powerpc/include/asm/thread_info.h index b0f200aba2b3..97f35f9b1a96 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 __ASSEMBLER__diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c index eb23966ac0a9..9237dcbeee4a 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 = ¤t->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-- 2.47.0