[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-ppc] [Qemu-devel] Why is "spapr-pci-host-bridge" no-user?
From: |
Markus Armbruster |
Subject: |
Re: [Qemu-ppc] [Qemu-devel] Why is "spapr-pci-host-bridge" no-user? |
Date: |
Fri, 03 Jun 2016 13:36:55 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) |
Alexey Kardashevskiy <address@hidden> writes:
> On 03/06/16 16:40, Markus Armbruster wrote:
>> Commit 09aa9a5 "spapr-pci: enable adding PHB via -device" set
>> cannot_instantiate_with_device_add_yet without also adding a comment
>> explaining why. It is currently the only one lacking such a comment.
>> Let's fix that.
>>
>> Unfortunately, the commit message doesn't tell me (or I'm too dense to
>> understand it):
>>
>> spapr-pci: enable adding PHB via -device
>>
>> Recent changes introduced cannot_instantiate_with_device_add_yet
>> and removed capability of adding yet another PCI host bridge via
>> command line for SPAPR platform (POWERPC64 server).
>>
>> This brings the capability back and puts SPAPR PHB into "bridge"
>> category.
>>
>> This is not much use for emulated PHB but it is absolutely required
>> for VFIO as we put an IOMMU group onto a separate PHB on SPAPR.
>>
>> Signed-off-by: Alexey Kardashevskiy <address@hidden>
>> Signed-off-by: Alexander Graf <address@hidden>
>>
>> Alexey, can you explain why the device cannot be used with -device /
>> device_add?
>
> It can be used with "-device" with as it is today, i.e. with
> "cannot_instantiate_with_device_add_yet=false".
I misread the code. But the assignment needs an explanation anyway :)
> With "cannot_instantiate_with_device_add_yet=true", I get this:
>
> qemu-system-ppc64: -device spapr-pci-host-bridge,id=phb10,index=10:
> Parameter 'driver' expects pluggable device type
>
>
> At that moment (sha1 09aa9a526a86fd2e380e86^) it failed because of
> inherited "cannot_instantiate_with_device_add_yet=true" from
> sysbus_device_class_init() (which is gone now):
>
> qemu-system-ppc64: -device spapr-pci-host-bridge,id=phb10,index=10:
> Parameter 'driver' expects pluggable device type
>
> So there was my patch.
>
>
> "device_add" is different, it does not work because:
> (qemu) device_add spapr-pci-host-bridge
> Bus 'main-system-bus' does not support hotplugging
>
> Which I am not sure if it is true for all platforms or just spapr/ppc64 but
> I do not care much now as there is some work to do anyway to support PHB
> hotplug as per LoPAPR specification anyway.
>
> Does this help? :)
Now you made me read the code more carefully, I have different
questions.
Can we delete the assignment? -device
spapr-pci-host-bridge,id=phb10,index=10 still works for me then.
If not, why?