From: Lai Jiangshan <jiangshanlai@gmail.com>
To: linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Sean Christopherson <seanjc@google.com>,
Lai Jiangshan <laijs@linux.alibaba.com>,
stable@vger.kernel.org
Subject: [PATCH V2] kvm: check tlbs_dirty directly
Date: Tue, 15 Dec 2020 22:52:59 +0800 [thread overview]
Message-ID: <20201215145259.18684-1-jiangshanlai@gmail.com> (raw)
In-Reply-To: <ea0938d2-f766-99de-2019-9daf5798ccac@redhat.com>
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);
--
2.19.1.6.gb485710b
next prev parent reply other threads:[~2020-12-15 13:53 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-13 4:49 [PATCH] kvm: don't lose the higher 32 bits of tlbs_dirty Lai Jiangshan
2020-12-14 17:20 ` Sean Christopherson
2020-12-15 5:14 ` Lai Jiangshan
2020-12-15 10:32 ` Paolo Bonzini
2020-12-15 14:52 ` Lai Jiangshan [this message]
2020-12-15 18:44 ` [PATCH V2] kvm: check tlbs_dirty directly Sean Christopherson
2020-12-16 9:46 ` Greg KH
2020-12-16 16:37 ` Paolo Bonzini
2020-12-17 15:41 ` [PATCH V3] " Lai Jiangshan
2020-12-21 18:31 ` Paolo Bonzini
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