linux-kernel - [RFC PATCH 1/3] mm/mmu_notifier: introduce a new mmu notifier flag MMU_NOTIFIER_RANGE

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Date:   Tue,  8 Aug 2023 15:14:48 +0800
From:   Yan Zhao <yan.y.zhao@...el.com>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     pbonzini@...hat.com, seanjc@...gle.com, mike.kravetz@...cle.com,
        apopple@...dia.com, jgg@...dia.com, rppt@...nel.org,
        akpm@...ux-foundation.org, kevin.tian@...el.com,
        Yan Zhao <yan.y.zhao@...el.com>
Subject: [RFC PATCH 1/3] mm/mmu_notifier: introduce a new mmu notifier flag MMU_NOTIFIER_RANGE_NUMA

Introduce a new mmu notifier flag MMU_NOTIFIER_RANGE_NUMA to indicate the
notification of MMU_NOTIFY_PROTECTION_VMA is for NUMA balance purpose
specifically.

So that, the subscriber of mmu notifier, like KVM, can do some
performance optimization according to this accurate information.

Signed-off-by: Yan Zhao <yan.y.zhao@...el.com>
---
 include/linux/mmu_notifier.h | 1 +
 mm/mprotect.c                | 4 +++-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
index 64a3e051c3c4..a6dc829a4bce 100644
--- a/include/linux/mmu_notifier.h
+++ b/include/linux/mmu_notifier.h
@@ -60,6 +60,7 @@ enum mmu_notifier_event {
 };
 
 #define MMU_NOTIFIER_RANGE_BLOCKABLE (1 << 0)
+#define MMU_NOTIFIER_RANGE_NUMA (1 << 1)
 
 struct mmu_notifier_ops {
 	/*
diff --git a/mm/mprotect.c b/mm/mprotect.c
index 6f658d483704..cb99a7d66467 100644
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -381,7 +381,9 @@ static inline long change_pmd_range(struct mmu_gather *tlb,
 		/* invoke the mmu notifier if the pmd is populated */
 		if (!range.start) {
 			mmu_notifier_range_init(&range,
-				MMU_NOTIFY_PROTECTION_VMA, 0,
+				MMU_NOTIFY_PROTECTION_VMA,
+				cp_flags & MM_CP_PROT_NUMA ?
+				MMU_NOTIFIER_RANGE_NUMA : 0,
 				vma->vm_mm, addr, end);
 			mmu_notifier_invalidate_range_start(&range);
 		}
-- 
2.17.1