linux-kernel - [PATCH 03/13] KVM: WARN if *any* MMU invalidation sequence doesn't add a range

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Date:   Thu, 21 Sep 2023 13:33:20 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        Michael Roth <michael.roth@....com>,
        Binbin Wu <binbin.wu@...ux.intel.com>
Subject: [PATCH 03/13] KVM: WARN if *any* MMU invalidation sequence doesn't
 add a range

Tweak the assertion in kvm_mmu_invalidate_end() to unconditionally require
a range to be added between start() and end().  Asserting if and only if
kvm->mmu_invalidate_in_progress is non-zero makes the assertion all but
useless as it would fire only when there are multiple invalidations in
flight, which is not common and would also get a false negative if one or
more sequences, but not all, added a range.

Reported-by: Binbin Wu <binbin.wu@...ux.intel.com>
Fixes: 145725d1542a ("KVM: Use gfn instead of hva for mmu_notifier_retry")
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 virt/kvm/kvm_main.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 30708e460568..54480655bcce 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -873,11 +873,10 @@ void kvm_mmu_invalidate_end(struct kvm *kvm)
 	KVM_BUG_ON(kvm->mmu_invalidate_in_progress < 0, kvm);
 
 	/*
-	 * Assert that at least one range must be added between start() and
-	 * end().  Not adding a range isn't fatal, but it is a KVM bug.
+	 * Assert that at least one range was added between start() and end().
+	 * Not adding a range isn't fatal, but it is a KVM bug.
 	 */
-	WARN_ON_ONCE(kvm->mmu_invalidate_in_progress &&
-		     kvm->mmu_invalidate_range_start == INVALID_GPA);
+	WARN_ON_ONCE(kvm->mmu_invalidate_range_start == INVALID_GPA);
 }
 
 static void kvm_mmu_notifier_invalidate_range_end(struct mmu_notifier *mn,
-- 
2.42.0.515.g380fc7ccd1-goog