On 2024/6/14 上午12:43, Sean Christopherson wrote:
On Thu, Jun 13, 2024, Bibo Mao wrote:
Function kvm_reset_dirty_gfn may be called with parameters cur_slot /
cur_offset / mask are all zero, it does not represent real dirty page.
It is not necessary to clear dirty page in this condition. Also return
value of macro __fls() is undefined if mask is zero which is called in
funciton kvm_reset_dirty_gfn(). Here just discard it.
Signed-off-by: Bibo Mao <maobibo@xxxxxxxxxxx>
---
virt/kvm/dirty_ring.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/virt/kvm/dirty_ring.c b/virt/kvm/dirty_ring.c
index 86d267db87bb..05f4c1c40cc7 100644
--- a/virt/kvm/dirty_ring.c
+++ b/virt/kvm/dirty_ring.c
@@ -147,14 +147,16 @@ int kvm_dirty_ring_reset(struct kvm *kvm, struct kvm_dirty_ring *ring)
continue;
}
}
- kvm_reset_dirty_gfn(kvm, cur_slot, cur_offset, mask);
+ if (mask)
+ kvm_reset_dirty_gfn(kvm, cur_slot, cur_offset, mask);
cur_slot = next_slot;
cur_offset = next_offset;
mask = 1;
first_round = false;
}
- kvm_reset_dirty_gfn(kvm, cur_slot, cur_offset, mask);
+ if (mask)
+ kvm_reset_dirty_gfn(kvm, cur_slot, cur_offset, mask);
Given that mask must be checked before __fls(), just do:
That is ok for me. To be frankly I am not familiar with kvm common code,
I submit this patch just when I look through the migration source code.
Regards
Bibo Mao
diff --git a/virt/kvm/dirty_ring.c b/virt/kvm/dirty_ring.c
index 86d267db87bb..7bc74969a819 100644
--- a/virt/kvm/dirty_ring.c
+++ b/virt/kvm/dirty_ring.c
@@ -55,6 +55,9 @@ static void kvm_reset_dirty_gfn(struct kvm *kvm, u32 slot, u64 offset, u64 mask)
struct kvm_memory_slot *memslot;
int as_id, id;
+ if (!mask)
+ return;
+
as_id = slot >> 16;
id = (u16)slot;
