From 676f819c3e982db3695a371f336a05086585ea4f Mon Sep 17 00:00:00 2001
From: Bibo Mao <maobibo@loongson.cn>
Date: Thu, 13 Jun 2024 20:28:03 +0800
Subject: [PATCH] KVM: Discard zero mask with function kvm_dirty_ring_reset

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 return.

Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Message-ID: <20240613122803.1031511-1-maobibo@loongson.cn>
[Move the conditional inside kvm_reset_dirty_gfn; suggested by
 Sean Christopherson. - Paolo]
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 virt/kvm/dirty_ring.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/virt/kvm/dirty_ring.c b/virt/kvm/dirty_ring.c
index 86d267db87bb1..7bc74969a819a 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;
 
-- 
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