From db7ed3f3b56a3caff78a300f7216c419e2015688 Mon Sep 17 00:00:00 2001
From: Paolo Bonzini <pbonzini@redhat.com>
Date: Mon, 22 Nov 2021 19:50:28 -0500
Subject: [PATCH 1/6] KVM: SEV: do not use list_replace_init on an empty list
Git-commit: 4674164f0ac5fd553c38b2b8c49fe13297fed38b 
Patch-mainline: 5.16-rc4
References: bsc#1194526

list_replace_init cannot be used if the source is an empty list,
because "new->next->prev = new" will overwrite "old->next":

				new				old
				prev = new, next = new		prev = old, next = old
new->next = old->next		prev = new, next = old		prev = old, next = old
new->next->prev = new		prev = new, next = old		prev = old, next = new
new->prev = old->prev		prev = old, next = old		prev = old, next = old
new->next->prev = new		prev = old, next = old		prev = new, next = new

The desired outcome instead would be to leave both old and new the same
as they were (two empty circular lists).  Use list_cut_before, which
already has the necessary check and is documented to discard the
previous contents of the list that will hold the result.

Fixes: b56639318bb2 ("KVM: SEV: Add support for SEV intra host migration")
Reviewed-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20211123005036.2954379-5-pbonzini@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Li Zhang <lizhang@suse.de>
---
 arch/x86/kvm/svm/sev.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 0c9a0c635bd5..d43242ba46c2 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1615,8 +1615,7 @@ static void sev_migrate_from(struct kvm_sev_info *dst,
 	src->handle = 0;
 	src->pages_locked = 0;
 
-	INIT_LIST_HEAD(&dst->regions_list);
-	list_replace_init(&src->regions_list, &dst->regions_list);
+	list_cut_before(&dst->regions_list, &src->regions_list, &src->regions_list);
 }
 
 static int sev_es_migrate_from(struct kvm *dst, struct kvm *src)
-- 
2.31.1