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Re: [Qemu-devel] [PATCH v2] qdev: Mark devices as non-hotpluggable by de
From: |
Eduardo Habkost |
Subject: |
Re: [Qemu-devel] [PATCH v2] qdev: Mark devices as non-hotpluggable by default |
Date: |
Mon, 25 Sep 2017 10:31:53 -0300 |
User-agent: |
Mutt/1.8.3 (2017-05-23) |
On Mon, Sep 25, 2017 at 01:53:16PM +0200, Cornelia Huck wrote:
> On Fri, 22 Sep 2017 11:16:34 +0200
> Thomas Huth <address@hidden> wrote:
>
> > Historically we've marked all devices as hotpluggable by default. However,
> > most devices are not hotpluggable, and you also need a HotplugHandler to
> > support these devices. So if the user tries to "device_add" or "device_del"
> > such a non-hotpluggable device during runtime, either nothing really usable
> > happens, or QEMU even crashes/aborts unexpectedly (see for example commit
> > 84ebd3e8c7d4fe955b - "Mark diag288 watchdog as non-hotpluggable").
> > So let's change this dangerous default behaviour and mark the devices as
> > non-hotpluggable by default. Certain parent devices classes which are known
> > as hotpluggable (e.g. PCI, USB, etc.) are marked with "hotpluggable = true",
> > so that devices that are derived from these classes continue to work as
> > expected.
> >
> > Signed-off-by: Thomas Huth <address@hidden>
> > ---
> > v2: Add missing devices and dropped "RFC" status. See Eduardo's reply on
> > the previous version of this patch for the rationale which devices need
> > to be hotpluggable:
> > https://lists.gnu.org/archive/html/qemu-devel/2017-09/msg06128.html
> >
> > hw/char/virtio-serial-bus.c | 1 +
> > hw/core/qdev.c | 10 ++++------
> > hw/mem/nvdimm.c | 3 +++
> > hw/mem/pc-dimm.c | 1 +
> > hw/pci/pci.c | 1 +
> > hw/ppc/spapr_cpu_core.c | 1 +
> > hw/s390x/ccw-device.c | 1 +
> > hw/scsi/scsi-bus.c | 1 +
> > hw/usb/bus.c | 1 +
> > hw/usb/dev-smartcard-reader.c | 1 +
> > hw/xen/xen_backend.c | 1 +
> > target/i386/cpu.c | 4 ++--
> > target/s390x/cpu.c | 1 +
> > 13 files changed, 19 insertions(+), 8 deletions(-)
>
> Hm, this seems to break hotplug of virtio devices:
>
> (qemu) device_add virtio-net-pci,id=xxx
> Device 'virtio-net-device' does not support hotplugging
>
> (qemu) device_add virtio-net-ccw,id=yyy
> Device 'virtio-net-device' does not support hotplugging
>
> We probably need to enable hotplug for virtio devices as well?
I've seen a similar case broken by "[PATCH] hw/core/qdev: Do not
allow hot-plugging without hotplug controller", because we're
blocking creation of devices created internally by other devices,
not just the ones created by device_add. I need to find the
exact reproducer again.
It would probably simplify things if we move the check for
DeviceClass::hotpluggable to qmp_device_add(), instead of
device_set_realized().
--
Eduardo
- [Qemu-devel] [PATCH v2] qdev: Mark devices as non-hotpluggable by default, Thomas Huth, 2017/09/22
- Re: [Qemu-devel] [PATCH v2] qdev: Mark devices as non-hotpluggable by default, David Gibson, 2017/09/22
- Re: [Qemu-devel] [PATCH v2] qdev: Mark devices as non-hotpluggable by default, Marcel Apfelbaum, 2017/09/25
- Re: [Qemu-devel] [PATCH v2] qdev: Mark devices as non-hotpluggable by default, Cornelia Huck, 2017/09/25
- Re: [Qemu-devel] [PATCH v2] qdev: Mark devices as non-hotpluggable by default,
Eduardo Habkost <=
- Re: [Qemu-devel] [PATCH v2] qdev: Mark devices as non-hotpluggable by default, Igor Mammedov, 2017/09/25
- Re: [Qemu-devel] [PATCH v2] qdev: Mark devices as non-hotpluggable by default, Eduardo Habkost, 2017/09/25
- Re: [Qemu-devel] [PATCH v2] qdev: Mark devices as non-hotpluggable by default, Thomas Huth, 2017/09/25
- Re: [Qemu-devel] [PATCH v2] qdev: Mark devices as non-hotpluggable by default, Peter Maydell, 2017/09/25
- Re: [Qemu-devel] [PATCH v2] qdev: Mark devices as non-hotpluggable by default, Thomas Huth, 2017/09/25
- Re: [Qemu-devel] [PATCH v2] qdev: Mark devices as non-hotpluggable by default, Peter Maydell, 2017/09/25
- Re: [Qemu-devel] [PATCH v2] qdev: Mark devices as non-hotpluggable by default, Eduardo Habkost, 2017/09/25
- Re: [Qemu-devel] [PATCH v2] qdev: Mark devices as non-hotpluggable by default, Peter Maydell, 2017/09/25
- Re: [Qemu-devel] [PATCH v2] qdev: Mark devices as non-hotpluggable by default, Eduardo Habkost, 2017/09/25
- Re: [Qemu-devel] [PATCH v2] qdev: Mark devices as non-hotpluggable by default, Peter Maydell, 2017/09/25