[ 001/117] KVM: mmu_notifier: Flush TLBs before releasing mmu_lock

From: Ben Hutchings
Date: Sun May 27 2012 - 23:50:13 EST


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

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

From: Marcelo Tosatti <mtosatti@xxxxxxxxxx>

From: Takuya Yoshikawa <yoshikawa.takuya@xxxxxxxxxxxxx>

(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@xxxxxxxxxxxxx>
Signed-off-by: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
Signed-off-by: Avi Kivity <avi@xxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
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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