Re: [PATCH] KVM: document lock orders

From: Radim KrÄmÃÅ
Date: Thu Oct 13 2016 - 08:51:17 EST


2016-10-13 13:10+0200, Paolo Bonzini:
> This is long overdue, and not really hard.
>
> Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> ---

Applied to kvm/queue, thanks.

> 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
> ------------
> --
> 2.7.4
>