[PATCH v2 5/7] powerpc/mm: support nested lazy_mmu sections

Kevin Brodsky
2025-09-08T07:41:02Z

The lazy_mmu API now allows nested sections to be handled by arch
code: enter() can return a flag if called inside another lazy_mmu
section, so that the matching call to leave() leaves any
optimisation enabled.

This patch implements that new logic for powerpc: if there is an
active batch, then enter() returns LAZY_MMU_NESTED and the matching
leave() leaves batch->active set. The preempt_{enable,disable} calls
are left untouched as they already handle nesting themselves.

TLB flushing is still done in leave() regardless of the nesting
level, as the caller may rely on it whether nesting is occurring or
not.

Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com>
---
arch/powerpc/include/asm/book3s/64/tlbflush-hash.h | 13 ++++++++++---
1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h b/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h
index c9f1e819e567..e92bce2efca6 100644
--- a/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h
+++ b/arch/powerpc/include/asm/book3s/64/tlbflush-hash.h
@@ -39,9 +39,13 @@ static inline lazy_mmu_state_t arch_enter_lazy_mmu_mode(void)
*/
preempt_disable();
batch = this_cpu_ptr(&ppc64_tlb_batch);
- batch->active = 1;

- return LAZY_MMU_DEFAULT;
+ if (!batch->active) {
+ batch->active = 1;
+ return LAZY_MMU_DEFAULT;
+ } else {
+ return LAZY_MMU_NESTED;
+ }
}

static inline void arch_leave_lazy_mmu_mode(lazy_mmu_state_t state)
@@ -54,7 +58,10 @@ static inline void arch_leave_lazy_mmu_mode(lazy_mmu_state_t state)

if (batch->index)
__flush_tlb_pending(batch);
- batch->active = 0;
+
+ if (state != LAZY_MMU_NESTED)
+ batch->active = 0;
+
preempt_enable();
}

--
2.47.0