From: Sean Christopherson <seanjc@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, pgonda@google.com
Subject: Re: [PATCH 04/12] KVM: SEV: do not use list_replace_init on an empty list
Date: Mon, 29 Nov 2021 22:27:55 +0000 [thread overview]
Message-ID: <YaVT638kTtgF64/i@google.com> (raw)
In-Reply-To: <20211123005036.2954379-5-pbonzini@redhat.com>
On Mon, Nov 22, 2021, Paolo Bonzini wrote:
> 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")
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
> 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 21ac0a5de4e0..75955beb3770 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -1613,8 +1613,7 @@ 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);
Yeesh, that is tricky. A list_move_all() helper in list.h to do
list_cut_before(dst, src, src);
would be nice.
Reviewed-by: Sean Christopherson <seanjc@google.com>
> }
>
> static int sev_es_migrate_from(struct kvm *dst, struct kvm *src)
> --
> 2.27.0
>
>
next prev parent reply other threads:[~2021-11-29 22:28 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-23 0:50 [PATCH 00/12] Fixes for KVM_CAP_VM_MOVE/COPY_ENC_CONTEXT_FROM Paolo Bonzini
2021-11-23 0:50 ` [PATCH 01/12] selftests: fix check for circular KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM Paolo Bonzini
2021-12-01 15:52 ` Peter Gonda
2021-11-23 0:50 ` [PATCH 02/12] selftests: sev_migrate_tests: free all VMs Paolo Bonzini
2021-12-01 15:54 ` Peter Gonda
2021-11-23 0:50 ` [PATCH 03/12] KVM: SEV: expose KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM capability Paolo Bonzini
2021-11-29 22:28 ` Sean Christopherson
2021-12-01 15:55 ` Peter Gonda
2021-11-23 0:50 ` [PATCH 04/12] KVM: SEV: do not use list_replace_init on an empty list Paolo Bonzini
2021-11-29 22:27 ` Sean Christopherson [this message]
2021-11-23 0:50 ` [PATCH 05/12] KVM: SEV: cleanup locking for KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM Paolo Bonzini
2021-12-01 16:11 ` Peter Gonda
2021-11-23 0:50 ` [PATCH 06/12] KVM: SEV: initialize regions_list of a mirror VM Paolo Bonzini
2021-11-29 23:00 ` Sean Christopherson
2021-11-23 0:50 ` [PATCH 07/12] KVM: SEV: move mirror status to destination of KVM_CAP_VM_MOVE_ENC_CONTEXT_FROM Paolo Bonzini
2021-11-29 23:02 ` Sean Christopherson
2021-11-23 0:50 ` [PATCH 08/12] selftests: sev_migrate_tests: add tests for KVM_CAP_VM_COPY_ENC_CONTEXT_FROM Paolo Bonzini
2021-12-01 18:09 ` Peter Gonda
2021-12-07 20:11 ` Peter Gonda
2021-11-23 0:50 ` [PATCH 09/12] KVM: SEV: Do COPY_ENC_CONTEXT_FROM with both VMs locked Paolo Bonzini
2021-11-29 23:08 ` Sean Christopherson
2021-11-23 0:50 ` [PATCH 10/12] KVM: SEV: Prohibit migration of a VM that has mirrors Paolo Bonzini
2021-11-29 22:54 ` Sean Christopherson
2021-12-01 18:17 ` Peter Gonda
2021-12-01 18:21 ` Paolo Bonzini
2021-11-23 0:50 ` [PATCH 11/12] KVM: SEV: do not take kvm->lock when destroying Paolo Bonzini
2021-11-29 22:31 ` Sean Christopherson
2021-11-23 0:50 ` [PATCH 12/12] KVM: SEV: accept signals in sev_lock_two_vms Paolo Bonzini
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