linux-kernel - Re: [PATCHv3 3/4] kvm: convert bus to slots

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Date:	Mon, 29 Jun 2009 12:50:31 -0300
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	Gregory Haskins <ghaskins@...ell.com>, avi@...hat.com,
	kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
	paulmck@...ux.vnet.ibm.com, markmc@...hat.com
Subject: Re: [PATCHv3 3/4] kvm: convert bus to slots_lock

On Mon, Jun 29, 2009 at 03:09:11PM +0300, Michael S. Tsirkin wrote:
> Use slots_lock to protect device list on the bus.  slots_lock is already
> taken for read everywhere, so we only need to take it for write when
> registering devices.  This is in preparation to removing in_range and
> kvm->lock around it.
> 
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
> ---
>  arch/x86/kvm/i8254.c     |    4 ++--
>  arch/x86/kvm/i8259.c     |    2 +-
>  include/linux/kvm_host.h |    3 ++-
>  virt/kvm/ioapic.c        |    2 +-
>  virt/kvm/kvm_main.c      |    5 ++++-
>  5 files changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/kvm/i8254.c b/arch/x86/kvm/i8254.c
> index 331705f..c2387ec 100644
> --- a/arch/x86/kvm/i8254.c
> +++ b/arch/x86/kvm/i8254.c
> @@ -620,11 +620,11 @@ struct kvm_pit *kvm_create_pit(struct kvm *kvm, u32 flags)
>  	kvm_register_irq_mask_notifier(kvm, 0, &pit->mask_notifier);
>  
>  	kvm_iodevice_init(&pit->dev, &pit_dev_ops);
> -	kvm_io_bus_register_dev(&kvm->pio_bus, &pit->dev);
> +	kvm_io_bus_register_dev(kvm, &kvm->pio_bus, &pit->dev);
>  
>  	if (flags & KVM_PIT_SPEAKER_DUMMY) {
>  		kvm_iodevice_init(&pit->speaker_dev, &speaker_dev_ops);
> -		kvm_io_bus_register_dev(&kvm->pio_bus, &pit->speaker_dev);
> +		kvm_io_bus_register_dev(kvm, &kvm->pio_bus, &pit->speaker_dev);
>  	}
>  
>  	return pit;
> diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
> index 148c52a..1851aec 100644
> --- a/arch/x86/kvm/i8259.c
> +++ b/arch/x86/kvm/i8259.c
> @@ -548,6 +548,6 @@ struct kvm_pic *kvm_create_pic(struct kvm *kvm)
>  	 * Initialize PIO device
>  	 */
>  	kvm_iodevice_init(&s->dev, &picdev_ops);
> -	kvm_io_bus_register_dev(&kvm->pio_bus, &s->dev);
> +	kvm_io_bus_register_dev(kvm, &kvm->pio_bus, &s->dev);
>  	return s;

case KVM_CREATE_PIT2:
create_pit:
mutex_lock(&kvm->lock);
kvm_io_bus_register_dev
down_write(slots_lock);

But the order is slots_lock -> kvm->lock.

(you might want to update the comment on top of kvm_main.c to 
reflect that).

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