Re: [PATCH 0/5][RFC] more fine grained locking for IRQ injection

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Jul 13, 2009 at 12:12:30PM +0300, Gleb Natapov wrote:
> kvm->irq_lock protects too much stuff, but still fail to protect
> everything it was design to protect (see ack notifiers call in pic). I
> want to make IRQ injection logic use more fine grained locking.

At least irq routing changes and notifier list changes
do not seem to be involved in irq injection.
So why do we want fine-grained locking there?

> This patch
> series split kvm->irq_lock mutex to smaller spinlocks each one protects
> only one thing. Irq routing, irq notifier lists and ioapic gain their own
> spinlock.  pic is already uses its own lock. This patch series also makes
> interrupt injection to lapic lockless (several kvm_irq_delivery_to_apic()
> may run in parallel), but access to lapic was never fully locked in the
> first place. VCPU could access lapic in parallel with interrupt injection.
> 
> The patch series is on top of my previous series that converts ack notifiers
> to the RCU locking.
> 
> Gleb Natapov (5):
>   Protect irq_sources_bitmap by kvm->lock instead of kvm->irq_lock
>   Move irq routing to its own locking.
>   Move irq notifiers lists to its own locking.
>   Move IO APIC to its own lock.
>   Drop kvm->irq_lock lock.
> 
>  arch/ia64/kvm/kvm-ia64.c |   29 +++++++++++++++++++--------
>  arch/x86/kvm/i8254.c     |    4 +-
>  arch/x86/kvm/lapic.c     |    7 +-----
>  arch/x86/kvm/x86.c       |   32 +++++++++++++++++++-----------
>  include/linux/kvm_host.h |    3 +-
>  virt/kvm/eventfd.c       |    2 -
>  virt/kvm/ioapic.c        |   47 +++++++++++++++++++++++++++------------------
>  virt/kvm/ioapic.h        |    1 +
>  virt/kvm/irq_comm.c      |   35 ++++++++++++++-------------------
>  virt/kvm/kvm_main.c      |    7 ++---
>  10 files changed, 92 insertions(+), 75 deletions(-)
> 
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