diff options
author | Paolo Bonzini <pbonzini@redhat.com> | 2022-12-28 14:00:22 +0300 |
---|---|---|
committer | Paolo Bonzini <pbonzini@redhat.com> | 2022-12-28 14:02:54 +0300 |
commit | 02d9a04da453984b16f4a585ad808cf961df495e (patch) | |
tree | 86545ddca3d004a60878fa7d25377e1a537ac3d3 /Documentation/virt/kvm/locking.rst | |
parent | a79b53aaaab53de017517bf9579b6106397a523c (diff) | |
download | linux-02d9a04da453984b16f4a585ad808cf961df495e.tar.xz |
Documentation: kvm: clarify SRCU locking order
Currently only the locking order of SRCU vs kvm->slots_arch_lock
and kvm->slots_lock is documented. Extend this to kvm->lock
since Xen emulation got it terribly wrong.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'Documentation/virt/kvm/locking.rst')
-rw-r--r-- | Documentation/virt/kvm/locking.rst | 19 |
1 files changed, 14 insertions, 5 deletions
diff --git a/Documentation/virt/kvm/locking.rst b/Documentation/virt/kvm/locking.rst index 845a561629f1..a3ca76f9be75 100644 --- a/Documentation/virt/kvm/locking.rst +++ b/Documentation/virt/kvm/locking.rst @@ -16,17 +16,26 @@ The acquisition orders for mutexes are as follows: - kvm->slots_lock is taken outside kvm->irq_lock, though acquiring them together is quite rare. -- Unlike kvm->slots_lock, kvm->slots_arch_lock is released before - synchronize_srcu(&kvm->srcu). Therefore kvm->slots_arch_lock - can be taken inside a kvm->srcu read-side critical section, - while kvm->slots_lock cannot. - - kvm->mn_active_invalidate_count ensures that pairs of invalidate_range_start() and invalidate_range_end() callbacks use the same memslots array. kvm->slots_lock and kvm->slots_arch_lock are taken on the waiting side in install_new_memslots, so MMU notifiers must not take either kvm->slots_lock or kvm->slots_arch_lock. +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``. + On x86: - vcpu->mutex is taken outside kvm->arch.hyperv.hv_lock |