Re: [Qemu-devel] [PATCH] Remove a detached device from qemu_device_opts.

[Minoru Usui]

Hi, William, Markus and other people.

On Wed, 23 Feb 2011 10:42:02 +0100
William Dauchy <address@hidden> wrote:

> Hi Minoru,
> 
> On Tue, Feb 15, 2011 at 3:32 AM, Minoru Usui <address@hidden> wrote:
> > I can reproduce, too.
> > But strangely, it don't occur in case of loading acpiphp driver
> > to the guest VM on below environment.
> >
> >  Host : RHEL6.0
> >  Guest: RHEL5.5
> >
> > Unfortunately, I'm not familiar with qemu-kvm.
> > I investigated below questions about this problem, but I couldn't resolve 
> > them.
> >
> >  - How to call qdev_free() asynchronously. (How should we fix this problem)
> >  - Why it don't occur with acpiphp driver
> >
> > If anyone knows answer of above questions or its clue, please let me know.
> 
> If fact this is not a bug.
> `qdev_free` is called when the acpi detach succeed in `pciej_write`.
> The virtual machine has to correctly support acpi signals.
> Please read the explanation from Markus Armbruster on
> http://lists.nongnu.org/archive/html/qemu-devel/2011-02/msg02637.html

William, Thank you for your help and telling me about it.

Markus, Thank you for your detailed explanation.
Basically, I understand behaviour of device_del command.
The result of pci hotunplug depends on behaviour of guest OS,
but device_del command doesn't wait hotunplug's result.

May I ask you a question?
Which device does qemu_device_opts manage?
just hotplugged to virtual machine? Or hotplugged to guest OS?

By the present implementation, device_add command adds qemu_device_opts 
immediately, 
whether guest OS can hotplug the device or not.
Nevertheless, device_del command waits for the device appropriately 
until it is hotunplugged by the guest OS.

By Markus's explanation, device_del command can't wait for the device
which hotunplugged from guest OS.
So, I feel it's better that qemu_device_opts manages the device
which hotplugged to guest OS.

If I am wrong, please let me know.
-- 
Minoru Usui <address@hidden>