Hi Greg,
On Mon, Jan 11, 2021 at 09:49:45AM +0100, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
>
> The patch below does not apply to the 4.19-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@xxxxxxxxxxxxxxx>.
Here is the backport.
--
Regards
Sudip
>From 17a6138c90d0816bb02f35a2600ffb67a00f64f7 Mon Sep 17 00:00:00 2001
From: Lai Jiangshan <laijs@xxxxxxxxxxxxxxxxx>
Date: Thu, 17 Dec 2020 23:41:18 +0800
Subject: [PATCH] kvm: check tlbs_dirty directly
commit 88bf56d04bc3564542049ec4ec168a8b60d0b48c upstream
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@xxxxxxxxxxxxxxx
Fixes: a4ee1ca4a36e ("KVM: MMU: delay flush all tlbs on sync_page path")
Signed-off-by: Lai Jiangshan <laijs@xxxxxxxxxxxxxxxxx>
Message-Id: <20201217154118.16497-1-jiangshanlai@xxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
[sudip: adjust context]
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@xxxxxxxxx>
---
virt/kvm/kvm_main.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 9312c7e750ed..1ecb27b3421a 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -412,9 +412,8 @@ static int kvm_mmu_notifier_invalidate_range_start(struct mmu_notifier *mn,
*/
kvm->mmu_notifier_count++;
need_tlb_flush = kvm_unmap_hva_range(kvm, start, end, blockable);
- 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);
--
2.30.0
