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.kis...@siemens.com>
---
Documentation/kvm/locking.txt | 30 ++++++++++++++++++++++++++++++
1 files changed, 30 insertions(+), 0 deletions(-)
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diff --git a/Documentation/kvm/locking.txt b/Documentation/kvm/locking.txt
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+KVM Lock Overview
+=================
+
+1. Acquisition Orders
+---------------------
+
+kvm_lock
++-> kvm::srcu / kvm::lock
+ +-> kvm::slots_lock
+ +-> kvm::mmu_lock
+...
+
+
+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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