Re: [PATCH] KVM: Start lock documentation

[Marcelo Tosatti <mtosatti@redhat.com>]

On Wed, Feb 09, 2011 at 03:11:28PM +0100, Jan Kiszka wrote:
> The goal of this document shall be
> - overview of all locks used in KVM core
> - provide details on the scope of each lock
> - explain the lock type, specifically of a raw spin locks
> - provide a lock ordering guide
> 
> Start with one dependency chain and two locks.
> 
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
> ---
>  Documentation/kvm/locking.txt |   30 ++++++++++++++++++++++++++++++
>  1 files changed, 30 insertions(+), 0 deletions(-)
>  create mode 100644 Documentation/kvm/locking.txt
> 
> diff --git a/Documentation/kvm/locking.txt b/Documentation/kvm/locking.txt
> new file mode 100644
> index 0000000..23f9092
> --- /dev/null
> +++ b/Documentation/kvm/locking.txt
> @@ -0,0 +1,30 @@
> +KVM Lock Overview
> +=================
> +
> +1. Acquisition Orders
> +---------------------
> +
> +kvm_lock
> ++-> kvm::srcu / kvm::lock
> +    +-> kvm::slots_lock
> +        +-> kvm::mmu_lock
> +...

Its not easy to understand what you mean here. What kvm_lock has to do
with the ordering described below it?

Other than that, "Reference" section structure is fine... (yeah, Avi has
been asking it for ages).

> +
> +2. Reference
> +------------
> +
> +Name:		kvm_lock
> +Type:		raw_spinlock
> +Arch:		any
> +Protects:	- vm_list
> +		- hardware virtualization enable/disable
> +Comment:	'raw' because hardware enabling/disabling must be atomic /wrt
> +		migration.
> +
> +Name:		kvm_arch::tsc_write_lock
> +Type:		raw_spinlock
> +Arch:		x86
> +Protects:	- kvm_arch::{last_tsc_write,last_tsc_nsec,last_tsc_offset}
> +		- tsc offset in vmcb
> +Comment:	'raw' because updating the tsc offsets must not be preempted.
> -- 
> 1.7.1
> --
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