linux-kernel - [PATCH 02/21] KVM: x86/mmu: Replace comment with an actual lockdep assertion on mmu

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Date:   Thu,  2 Feb 2023 18:27:50 +0000
From:   Ben Gardon <bgardon@...gle.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     Paolo Bonzini <pbonzini@...hat.com>, Peter Xu <peterx@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        David Matlack <dmatlack@...gle.com>,
        Vipin Sharma <vipinsh@...gle.com>,
        Ricardo Koller <ricarkol@...gle.com>,
        Ben Gardon <bgardon@...gle.com>
Subject: [PATCH 02/21] KVM: x86/mmu: Replace comment with an actual lockdep
 assertion on mmu_lock

From: Sean Christopherson <seanjc@...gle.com>

Assert that mmu_lock is held for write in __walk_slot_rmaps() instead of
hoping the function comment will magically prevent introducing bugs.

Signed-off-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Ben Gardon <bgardon@...gle.com>
---
 arch/x86/kvm/mmu/mmu.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 09a0a2cc76bae..2ea8e58f83256 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5805,7 +5805,6 @@ typedef bool (*slot_rmaps_handler) (struct kvm *kvm,
 				    struct kvm_rmap_head *rmap_head,
 				    const struct kvm_memory_slot *slot);
 
-/* The caller should hold mmu-lock before calling this function. */
 static __always_inline bool __walk_slot_rmaps(struct kvm *kvm,
 					      const struct kvm_memory_slot *slot,
 					      slot_rmaps_handler fn,
@@ -5815,6 +5814,8 @@ static __always_inline bool __walk_slot_rmaps(struct kvm *kvm,
 {
 	struct slot_rmap_walk_iterator iterator;
 
+	lockdep_assert_held_write(&kvm->mmu_lock);
+
 	for_each_slot_rmap_range(slot, start_level, end_level, start_gfn,
 			end_gfn, &iterator) {
 		if (iterator.rmap)
-- 
2.39.1.519.gcb327c4b5f-goog