Re: [Qemu-devel] [RFC 0/9] Virtio-mmio refactoring.

Re: [Qemu-devel] [RFC 0/9] Virtio-mmio refactoring.

[Peter Maydell]

On 25 April 2012 06:54, Evgeny Voevodin <e.voevodin@samsung.com> wrote:
> In this patchset refactoring of virtio-mmio layer is made.
> Instead of creating virtio-blk-mmio, virtio-net-mmio, etc on the system bus
> we create virtio-blk, virtio-net, etc devices on the virtio-transport bus.
> To create virtio-transport bus virtio-mmio-transport device provided.
> Transport device plugs into virtio-mmio bus.
> To create virtio-mmio bus virtio-mmio-bridge device provided.

This seems to me to have one more layer than it needs. Why not just:
 create virtio-blk, virtio-net, etc on the virtio-transport bus
 To create virtio-transport bus, we create a virtio-mmio-transport
 device, and this device is a sysbus device.

ie why do you have separate "virtio-mmio-transport" and
"virtio-mmio-bridge" devices, and two different new buses ("virtio-mmio"
and "virtio-transport") rather than just "virtio-transport"?

-- PMM

Re: [Qemu-devel] [RFC 0/9] Virtio-mmio refactoring.

[Evgeny Voevodin]

On 03.05.2012 16:14, Peter Maydell wrote:
> On 25 April 2012 06:54, Evgeny Voevodin<e.voevodin@samsung.com>  wrote:
>> In this patchset refactoring of virtio-mmio layer is made.
>> Instead of creating virtio-blk-mmio, virtio-net-mmio, etc on the system bus
>> we create virtio-blk, virtio-net, etc devices on the virtio-transport bus.
>> To create virtio-transport bus virtio-mmio-transport device provided.
>> Transport device plugs into virtio-mmio bus.
>> To create virtio-mmio bus virtio-mmio-bridge device provided.
> This seems to me to have one more layer than it needs. Why not just:
>   create virtio-blk, virtio-net, etc on the virtio-transport bus
>   To create virtio-transport bus, we create a virtio-mmio-transport
>   device, and this device is a sysbus device.
>
> ie why do you have separate "virtio-mmio-transport" and
> "virtio-mmio-bridge" devices, and two different new buses ("virtio-mmio"
> and "virtio-transport") rather than just "virtio-transport"?
>
> -- PMM
>

Actually, the only necessity to have a bridge device is to count amount
of transport devices. Amount of transport devices we need to know because
we want to specify names to transport buses (virtio-mmio.0, 
virtio-mmio.1, ...).
If there is a way to find out amount of transport devices on sysbus (and 
on pci bus)
we don't need bridge device.
Maybe, there is also another way to specify bus names instead of just 
get parent bus name
and add transport device's index as a tail.

-- 
Kind regards,
Evgeny Voevodin,
Leading Software Engineer,
ASWG, Moscow R&D center, Samsung Electronics
e-mail: e.voevodin@samsung.com

Re: [Qemu-devel] [RFC 0/9] Virtio-mmio refactoring.

[Evgeny Voevodin]

On 04.05.2012 07:41, Evgeny Voevodin wrote:
> On 03.05.2012 16:14, Peter Maydell wrote:
>> On 25 April 2012 06:54, Evgeny Voevodin<e.voevodin@samsung.com> wrote:
>>> In this patchset refactoring of virtio-mmio layer is made.
>>> Instead of creating virtio-blk-mmio, virtio-net-mmio, etc on the
>>> system bus
>>> we create virtio-blk, virtio-net, etc devices on the virtio-transport
>>> bus.
>>> To create virtio-transport bus virtio-mmio-transport device provided.
>>> Transport device plugs into virtio-mmio bus.
>>> To create virtio-mmio bus virtio-mmio-bridge device provided.
>> This seems to me to have one more layer than it needs. Why not just:
>> create virtio-blk, virtio-net, etc on the virtio-transport bus
>> To create virtio-transport bus, we create a virtio-mmio-transport
>> device, and this device is a sysbus device.
>>
>> ie why do you have separate "virtio-mmio-transport" and
>> "virtio-mmio-bridge" devices, and two different new buses ("virtio-mmio"
>> and "virtio-transport") rather than just "virtio-transport"?
>>
>> -- PMM
>>
>
> Actually, the only necessity to have a bridge device is to count amount
> of transport devices. Amount of transport devices we need to know because
> we want to specify names to transport buses (virtio-mmio.0,
> virtio-mmio.1, ...).
> If there is a way to find out amount of transport devices on sysbus (and
> on pci bus)
> we don't need bridge device.
> Maybe, there is also another way to specify bus names instead of just
> get parent bus name
> and add transport device's index as a tail.
>

Ok, seems that we don't need that bridge device. Each transport device
can run through all childs of parent bus and look if they have created 
virtio bus and then specify appropriate name to its virtio bus.

-- 
Kind regards,
Evgeny Voevodin,
Leading Software Engineer,
ASWG, Moscow R&D center, Samsung Electronics
e-mail: e.voevodin@samsung.com

Re: [Qemu-devel] [RFC 0/9] Virtio-mmio refactoring.

[Anthony Liguori]

On 05/03/2012 07:14 AM, Peter Maydell wrote:
> On 25 April 2012 06:54, Evgeny Voevodin<e.voevodin@samsung.com>  wrote:
>> In this patchset refactoring of virtio-mmio layer is made.
>> Instead of creating virtio-blk-mmio, virtio-net-mmio, etc on the system bus
>> we create virtio-blk, virtio-net, etc devices on the virtio-transport bus.
>> To create virtio-transport bus virtio-mmio-transport device provided.
>> Transport device plugs into virtio-mmio bus.
>> To create virtio-mmio bus virtio-mmio-bridge device provided.
>
> This seems to me to have one more layer than it needs. Why not just:
>   create virtio-blk, virtio-net, etc on the virtio-transport bus
>   To create virtio-transport bus, we create a virtio-mmio-transport
>   device, and this device is a sysbus device.
>
> ie why do you have separate "virtio-mmio-transport" and
> "virtio-mmio-bridge" devices, and two different new buses ("virtio-mmio"
> and "virtio-transport") rather than just "virtio-transport"?

I think using a bus won't work.   You need to create a VirtioDevice that has a 
link<VirtioTransport>.  I would suggest making VirtioTransport an interface.

Then you can have VirtioPCI inherit from PCIDevice and implement VirtioTransport.

Regards,

Anthony Liguori

>
> -- PMM
>

Re: [Qemu-devel] [RFC 0/9] Virtio-mmio refactoring.

[Evgeny Voevodin]

On 04.05.2012 17:19, Anthony Liguori wrote:
> On 05/03/2012 07:14 AM, Peter Maydell wrote:
>> On 25 April 2012 06:54, Evgeny Voevodin<e.voevodin@samsung.com>  wrote:
>>> In this patchset refactoring of virtio-mmio layer is made.
>>> Instead of creating virtio-blk-mmio, virtio-net-mmio, etc on the 
>>> system bus
>>> we create virtio-blk, virtio-net, etc devices on the 
>>> virtio-transport bus.
>>> To create virtio-transport bus virtio-mmio-transport device provided.
>>> Transport device plugs into virtio-mmio bus.
>>> To create virtio-mmio bus virtio-mmio-bridge device provided.
>>
>> This seems to me to have one more layer than it needs. Why not just:
>>   create virtio-blk, virtio-net, etc on the virtio-transport bus
>>   To create virtio-transport bus, we create a virtio-mmio-transport
>>   device, and this device is a sysbus device.
>>
>> ie why do you have separate "virtio-mmio-transport" and
>> "virtio-mmio-bridge" devices, and two different new buses ("virtio-mmio"
>> and "virtio-transport") rather than just "virtio-transport"?
>
> I think using a bus won't work.   You need to create a VirtioDevice 
> that has a link<VirtioTransport>.  I would suggest making 
> VirtioTransport an interface.

Do you mean latest QOM series that qomyfies buses or some issue in pci 
(which I don't see)?
I was planning to refactor virtio-pci, make sure it works and then 
hoping that last QOM series lands in master
convert all the stuff to correspond it.
>
> Then you can have VirtioPCI inherit from PCIDevice and implement 
> VirtioTransport.

-- 
Kind regards,
Evgeny Voevodin,
Leading Software Engineer,
ASWG, Moscow R&D center, Samsung Electronics
e-mail: e.voevodin@samsung.com