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-rw-r--r--Documentation/virt/kvm/locking.rst25
1 files changed, 13 insertions, 12 deletions
diff --git a/Documentation/virt/kvm/locking.rst b/Documentation/virt/kvm/locking.rst
index a3ca76f9be75..a0146793d197 100644
--- a/Documentation/virt/kvm/locking.rst
+++ b/Documentation/virt/kvm/locking.rst
@@ -24,21 +24,22 @@ The acquisition orders for mutexes are as follows:
For SRCU:
-- ``synchronize_srcu(&kvm->srcu)`` is called _inside_
- the kvm->slots_lock critical section, therefore kvm->slots_lock
- cannot be taken inside a kvm->srcu read-side critical section.
- Instead, kvm->slots_arch_lock is released before the call
- to ``synchronize_srcu()`` and _can_ be taken inside a
- kvm->srcu read-side critical section.
-
-- kvm->lock is taken inside kvm->srcu, therefore
- ``synchronize_srcu(&kvm->srcu)`` cannot be called inside
- a kvm->lock critical section. If you cannot delay the
- call until after kvm->lock is released, use ``call_srcu``.
+- ``synchronize_srcu(&kvm->srcu)`` is called inside critical sections
+ for kvm->lock, vcpu->mutex and kvm->slots_lock. These locks _cannot_
+ be taken inside a kvm->srcu read-side critical section; that is, the
+ following is broken::
+
+ srcu_read_lock(&kvm->srcu);
+ mutex_lock(&kvm->slots_lock);
+
+- kvm->slots_arch_lock instead is released before the call to
+ ``synchronize_srcu()``. It _can_ therefore be taken inside a
+ kvm->srcu read-side critical section, for example while processing
+ a vmexit.
On x86:
-- vcpu->mutex is taken outside kvm->arch.hyperv.hv_lock
+- vcpu->mutex is taken outside kvm->arch.hyperv.hv_lock and kvm->arch.xen.xen_lock
- kvm->arch.mmu_lock is an rwlock. kvm->arch.tdp_mmu_pages_lock and
kvm->arch.mmu_unsync_pages_lock are taken inside kvm->arch.mmu_lock, and