From: Lai Jiangshan laijs@linux.alibaba.com
In kvm_mmu_notifier_invalidate_range_start(), tlbs_dirty is used as: need_tlb_flush |= kvm->tlbs_dirty; with need_tlb_flush's type being int and tlbs_dirty's type being long.
It means that tlbs_dirty is always used as int and the higher 32 bits is useless. We need to check tlbs_dirty in a correct way and this change checks it directly without propagating it to need_tlb_flush.
And need_tlb_flush is changed to boolean because it is used as a boolean and its name starts with "need".
Note: it's _extremely_ unlikely this neglecting of higher 32 bits can cause problems in practice. It would require encountering tlbs_dirty on a 4 billion count boundary, and KVM would need to be using shadow paging or be running a nested guest.
Cc: stable@vger.kernel.org Fixes: a4ee1ca4a36e ("KVM: MMU: delay flush all tlbs on sync_page path") Signed-off-by: Lai Jiangshan laijs@linux.alibaba.com --- Changed from V1: Update the patch and the changelog as Sean Christopherson suggested.
virt/kvm/kvm_main.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 2541a17ff1c4..1c17f3d073cb 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -470,7 +470,8 @@ static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn, const struct mmu_notifier_range *range) { struct kvm *kvm = mmu_notifier_to_kvm(mn); - int need_tlb_flush = 0, idx; + int idx; + bool need_tlb_flush;
idx = srcu_read_lock(&kvm->srcu); spin_lock(&kvm->mmu_lock); @@ -480,11 +481,10 @@ static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn, * count is also read inside the mmu_lock critical section. */ kvm->mmu_notifier_count++; - need_tlb_flush = kvm_unmap_hva_range(kvm, range->start, range->end, - range->flags); - need_tlb_flush |= kvm->tlbs_dirty; + need_tlb_flush = !!kvm_unmap_hva_range(kvm, range->start, range->end, + range->flags); /* we've to flush the tlb before the pages can be freed */ - if (need_tlb_flush) + if (need_tlb_flush || kvm->tlbs_dirty) kvm_flush_remote_tlbs(kvm);
spin_unlock(&kvm->mmu_lock);