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Re: [Qemu-devel] [PATCH v2] qdev: Keep global allocation counter per bus


From: Markus Armbruster
Subject: Re: [Qemu-devel] [PATCH v2] qdev: Keep global allocation counter per bus
Date: Wed, 08 Jan 2014 15:35:56 +0100
User-agent: Gnus/5.13 (Gnus v5.13) Emacs/24.2 (gnu/linux)

Paolo Bonzini <address@hidden> writes:

> Leaving only those that will be affected by the patch:

You omitted akita, borzoi, connex, mainstone, nuri, smdkc210, spitz,
terrier, tosa, verdex, z2, s390-virtio.  Why won't they be affected?

You also omitted the machines that I can't get to start, but I'm not
overly worried by them, because they're all either Xen, where I don't
expect differences to plain x86, or ppcemb, where Alex gets to clean up
any mess he might make.

> Il 07/01/2014 18:34, Markus Armbruster ha scritto:
>>     target      machine         bus id              times
>>     aarch64     n800            i2c-bus.0           2
>>     aarch64     n810            i2c-bus.0           2
>>     arm         n800            i2c-bus.0           2
>>     arm         n810            i2c-bus.0           2
>
> Devices are created explicitly on one of the two buses, using
> s->mpu->i2c[0], so no change to the guest.
>
>>     aarch64     vexpress-a15    virtio-mmio-bus.0   4
>>     aarch64     vexpress-a9     virtio-mmio-bus.0   4
>>     aarch64     virt            virtio-mmio-bus.0   32
>>     arm         vexpress-a15    virtio-mmio-bus.0   4
>>     arm         vexpress-a9     virtio-mmio-bus.0   4
>>     arm         virt            virtio-mmio-bus.0   32
>
> With Alex's patch we get the ability to plug the device in a particular
> slot.  If anyone was using virtio-mmio-bus.0 explicitly, they get the
> first slot instead of the 4th or 32nd.  Bugfix.

Doesn't this break migration?  If yes, do we care?

>>     aarch64     xilinx-zynq-a9  usb-bus.0           2
>>     arm         xilinx-zynq-a9  usb-bus.0           2
>>     mips64el    fulong2e        usb-bus.0           2
>
> With Alex's patch we get the ability to plug the device in a particular
> controller.  If anyone was using usb-bus.0 explicitly, they get the
> "other" controller.  Guest visible change and not really a bugfix but it
> doesn't break working configurations (the position of USB devices should
> not be part of a device tree or firmware blob).  It may break migration.
>
>>     i386        isapc           ide.0               2
>>     x86_64      isapc           ide.0               2
>
> (Ugly) fix in Alex's patch.  The macio approach (using QOM children) is
> better.  No need for a perfect fix now.

I'm fine with Alex's ugly fix.

>>     mips        mips            ide.0               2
>>     mips64      mips            ide.0               2
>>     mips64el    mips            ide.0               2
>>     mipsel      mips            ide.0               2
>
> Not affected, the bus is not stored anywhere.

Isn't command line use and migration affected, just like everywhere
else?

>>     ppc         g3beige         ide.0               2
>>     ppc         mac99           ide.0               2
>>     ppc         prep            ide.0               2
>>     ppc64       g3beige         ide.0               2
>>     ppc64       mac99           ide.0               2
>>     ppc64       prep            ide.0               2
>
> Trusting Alex's tests here.

Our analysis should be recorded in the commit message.  With that done,
I could R-by the patch.



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