linux-kernel - [ 001/117] KVM: mmu_notifier: Flush TLBs before releasing mmu

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Message-Id: <20120528031203.013255424@decadent.org.uk>
Date:	Mon, 28 May 2012 04:12:03 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, Marcelo Tosatti <mtosatti@...hat.com>,
	Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>,
	Avi Kivity <avi@...hat.com>
Subject: [ 001/117] KVM: mmu_notifier: Flush TLBs before releasing mmu_lock

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Marcelo Tosatti <mtosatti@...hat.com>

From: Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>

(cherry picked from commit 565f3be2174611f364405bbea2d86e153c2e7e78

Other threads may process the same page in that small window and skip
TLB flush and then return before these functions do flush.

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@....ntt.co.jp>
Signed-off-by: Marcelo Tosatti <mtosatti@...hat.com>
Signed-off-by: Avi Kivity <avi@...hat.com>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 virt/kvm/kvm_main.c |   19 ++++++++++---------
 1 files changed, 10 insertions(+), 9 deletions(-)

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index e401c1b..9ffac2e 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -289,15 +289,15 @@ static void kvm_mmu_notifier_invalidate_page(struct mmu_notifier *mn,
 	 */
 	idx = srcu_read_lock(&kvm->srcu);
 	spin_lock(&kvm->mmu_lock);
+
 	kvm->mmu_notifier_seq++;
 	need_tlb_flush = kvm_unmap_hva(kvm, address) | kvm->tlbs_dirty;
-	spin_unlock(&kvm->mmu_lock);
-	srcu_read_unlock(&kvm->srcu, idx);
-
 	/* we've to flush the tlb before the pages can be freed */
 	if (need_tlb_flush)
 		kvm_flush_remote_tlbs(kvm);
 
+	spin_unlock(&kvm->mmu_lock);
+	srcu_read_unlock(&kvm->srcu, idx);
 }
 
 static void kvm_mmu_notifier_change_pte(struct mmu_notifier *mn,
@@ -335,12 +335,12 @@ static void kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
 	for (; start < end; start += PAGE_SIZE)
 		need_tlb_flush |= kvm_unmap_hva(kvm, start);
 	need_tlb_flush |= kvm->tlbs_dirty;
-	spin_unlock(&kvm->mmu_lock);
-	srcu_read_unlock(&kvm->srcu, idx);
-
 	/* we've to flush the tlb before the pages can be freed */
 	if (need_tlb_flush)
 		kvm_flush_remote_tlbs(kvm);
+
+	spin_unlock(&kvm->mmu_lock);
+	srcu_read_unlock(&kvm->srcu, idx);
 }
 
 static void kvm_mmu_notifier_invalidate_range_end(struct mmu_notifier *mn,
@@ -378,13 +378,14 @@ static int kvm_mmu_notifier_clear_flush_young(struct mmu_notifier *mn,
 
 	idx = srcu_read_lock(&kvm->srcu);
 	spin_lock(&kvm->mmu_lock);
-	young = kvm_age_hva(kvm, address);
-	spin_unlock(&kvm->mmu_lock);
-	srcu_read_unlock(&kvm->srcu, idx);
 
+	young = kvm_age_hva(kvm, address);
 	if (young)
 		kvm_flush_remote_tlbs(kvm);
 
+	spin_unlock(&kvm->mmu_lock);
+	srcu_read_unlock(&kvm->srcu, idx);
+
 	return young;
 }
 


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