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Re: [Qemu-devel] [PATCH 01/15] qdev: do not reset a device until the par
From: |
Michael S. Tsirkin |
Subject: |
Re: [Qemu-devel] [PATCH 01/15] qdev: do not reset a device until the parent has been initialized |
Date: |
Mon, 17 Dec 2012 18:53:41 +0200 |
On Mon, Dec 17, 2012 at 06:52:03PM +0200, Michael S. Tsirkin wrote:
> On Mon, Dec 17, 2012 at 05:24:36PM +0100, Paolo Bonzini wrote:
> > When a device creates a bus and more devices as part of its init callback,
> > the
> > child device could be reset while the parent is still only partly
> > initialized.
> > In this case, the right thing to do is to delay resetting the child. Do not
> > do it at all in qdev_init, instead use qdev_reset_all to reset
> > already-created
> > devices when the state goes from CREATED to INITIALIZED.
> >
> > This happens when hotplugging a usb-storage device. Without this patch,
> > initialization of a hotplugged usb-storage device would run in pre-order.
> > Initialization of a coldplugged usb-storage device would run according to
> > qdev_reset_all semantics (pre-order right now, post-order later in the
> > series).
>
> Is this a problem or just not pretty?
>
> > This patch makes things consistent.
> >
> > Signed-off-by: Paolo Bonzini <address@hidden>
> > ---
> > hw/qdev.c | 5 +++--
> > 1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/hw/qdev.c b/hw/qdev.c
> > index 599382c..2fdf4ac 100644
> > --- a/hw/qdev.c
> > +++ b/hw/qdev.c
> > @@ -176,8 +176,9 @@ int qdev_init(DeviceState *dev)
> > dev->alias_required_for_version);
> > }
> > dev->state = DEV_STATE_INITIALIZED;
> > - if (dev->hotplugged) {
> > - device_reset(dev);
> > + if (dev->hotplugged &&
> > + dev->parent_bus->parent->state == DEV_STATE_INITIALIZED) {
> > + qdev_reset_all(dev);
>
> Let's add a comment explaining the why of this test, and when
> will reset happen if it does not trigger here.
Also - shouldn't device init be delayed as well?
What do you think?
> > }
> > return 0;
> > }
> > --
> > 1.8.0.2
> >
- [Qemu-devel] [PATCH 00/15] qdev: make reset semantics more clear and consistent, reset qbuses under virtio devices, Paolo Bonzini, 2012/12/17
- [Qemu-devel] [PATCH 03/15] pci: clean up resetting of IRQs, Paolo Bonzini, 2012/12/17
- [Qemu-devel] [PATCH 05/15] virtio-s390: add a reset function to virtio-s390 devices, Paolo Bonzini, 2012/12/17
- [Qemu-devel] [PATCH 06/15] qdev: add qbus_reset_all, Paolo Bonzini, 2012/12/17
- [Qemu-devel] [PATCH 04/15] virtio-pci: reset device before PCI layer, Paolo Bonzini, 2012/12/17
- [Qemu-devel] [PATCH 08/15] lsi: use qbus_reset_all to reset SCSI bus, Paolo Bonzini, 2012/12/17
- [Qemu-devel] [PATCH 07/15] pci: do not export pci_bus_reset, Paolo Bonzini, 2012/12/17
- [Qemu-devel] [PATCH 09/15] qdev: allow both pre- and post-order vists in qdev walking functions, Paolo Bonzini, 2012/12/17
- [Qemu-devel] [PATCH 10/15] qdev: switch reset to post-order, Paolo Bonzini, 2012/12/17