From 58e3948a87e39289aeda5753e9712092c8ca0745 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Thu, 13 Oct 2016 13:10:57 +0200 Subject: [PATCH] KVM: document lock orders This is long overdue, and not really hard. Signed-off-by: Paolo Bonzini Message-Id: <1476357057-17899-1-git-send-email-pbonzini@redhat.com> Signed-off-by: Paolo Bonzini --- Documentation/virtual/kvm/locking.txt | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/Documentation/virtual/kvm/locking.txt b/Documentation/virtual/kvm/locking.txt index f2491a8c68b4..e5dd9f4d6100 100644 --- a/Documentation/virtual/kvm/locking.txt +++ b/Documentation/virtual/kvm/locking.txt @@ -4,7 +4,17 @@ KVM Lock Overview 1. Acquisition Orders --------------------- -(to be written) +The acquisition orders for mutexes are as follows: + +- kvm->lock is taken outside vcpu->mutex + +- kvm->lock is taken outside kvm->slots_lock and kvm->irq_lock + +- kvm->slots_lock is taken outside kvm->irq_lock, though acquiring + them together is quite rare. + +For spinlocks, kvm_lock is taken outside kvm->mmu_lock. Everything +else is a leaf: no other lock is taken inside the critical sections. 2: Exception ------------ -- 2.20.1