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Re: [Qemu-devel] [RFC 1/4] [UNTESTED] xen: Don't force has_dynamic_sysbu


From: Peter Maydell
Subject: Re: [Qemu-devel] [RFC 1/4] [UNTESTED] xen: Don't force has_dynamic_sysbus on machine class
Date: Fri, 24 Mar 2017 10:09:03 +0000

On 24 March 2017 at 08:23, Juergen Gross <address@hidden> wrote:
> On 23/03/17 22:28, Eduardo Habkost wrote:
>> The xen-backend devices created by the Xen code are not supposed
>> to be treated as dynamic sysbus devices. This is an attempt to
>> change that and see what happens, but I couldn't test it because
>> I don't have a Xen host set up.
>>
>> If this patch breaks anything, this means we have a bug in
>> foreach_dynamic_sysbus_device(), which is supposed to return only
>> devices created using -device.
>>
>> The original code that sets has_dynamic_sysbus was added by
>> commit 3a6c9172ac5951e6dac2b3f6cbce3cfccdec5894, but I don't see
>> any comment explaining why it was necessary.
>
> xen-backend devices are created via qmp commands when attaching new
> pv-devices to a domain. They can be dynamically removed, too. Setting
> has_dynamic_sysbus was necessary to support this feature.

This seems like it ought to be handled by marking the xen-backend
devices as being ok-to-dynamically-create somehow, not by marking
the machine as supporting dynamic-sysbus (which it doesn't).
Maybe we don't have the necessary support code to do that though?

thanks
-- PMM



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