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kvm: check tlbs_dirty directly

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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.

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: a4ee1ca4a3 ("KVM: MMU: delay flush all tlbs on sync_page path")
Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com>
Message-Id: <20201217154118.16497-1-jiangshanlai@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Lai Jiangshan 2020-12-17 23:41:18 +08:00 committed by Paolo Bonzini
parent de7860c8a3
commit 88bf56d04b
1 changed files with 1 additions and 2 deletions
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3
virt/kvm/kvm_main.c
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@ -485,9 +485,8 @@ static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
kvm->mmu_notifier_count++;
need_tlb_flush = kvm_unmap_hva_range(kvm, range->start, range->end,
range->flags);
need_tlb_flush |= kvm->tlbs_dirty;
/* 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);