Re: [Qemu-devel] [PATCH] qdev: Skip non-existing properties when setting globals

[Eduardo Habkost]

On Fri, Jun 06, 2014 at 11:38:58PM +0200, Igor Mammedov wrote:
> On Fri, 6 Jun 2014 17:14:29 -0300
> Eduardo Habkost <address@hidden> wrote:
> 
> > This avoids QEMU from aborting on cases like this:
> > 
> >   $ ./install/bin/qemu-system-x86_64 -global cpu.foobar=5
> >   qemu-system-x86_64: Property '.foobar' not found
> >   Aborted (core dumped)
> That is expected behavior.

Why?

QEMU should never dump core due to user error.

QEMU should not abort when handling a device_add command due to user
error.

> 
> > 
> > The code sets dev->not_used if the property is not found as an effort to
> > to allow errors to be reported even if the device is hotpluggable, but
> > it won't catch all errors. We can't know the property is not going to be
> > available for hotpluggable devices, unless we actually try to create the
> > device.
> Instead of ignoring users errors, DeviceState should have async_error
> field which could be set by device_post_init() instead of aborting and
> later device_add could gracefully fail hotadd operation if error is set.
> 
> PS:
> initfn-s could also reuse this, instead of ignoring errors as they do now.

Your proposal sounds good, and would allow reporting error without
creating an object_new() variation that accepts Error**.

But I believe we need to choose what to do in the meantime, while we
don't have that mechanism implemented. Dumping core is not acceptable.
Exiting QEMU while handling device_add doesn't seem acceptable to me,
either.

-- 
Eduardo