Regarding MMIO

Regarding MMIO

[Venkateswara Rao Dokku]

Hi,

If we go through the DPDK code it is observed that we are using MMIO for
Virt-IO devices. But in the Virt-IO specification, it is written that from
Virt-IO 1.0 onwards only they are supporting MMIO, all previous versions
uses Port IO for RX/TX notifications.

So, If I use VirtIO 0.9, Can I get the MMIO based notifications for RX/TX
or is it supported only for Virt-IO 1.0 onwards?

-- 
Thanks & Regards,
Venkateswara Rao Dokku.

Re: Regarding MMIO

[Stephen Hemminger]

On Thu, 1 Oct 2015 09:51:42 +0530
Venkateswara Rao Dokku <dvrao.584@gmail.com> wrote:

> Hi,
> 
> If we go through the DPDK code it is observed that we are using MMIO for
> Virt-IO devices. But in the Virt-IO specification, it is written that from
> Virt-IO 1.0 onwards only they are supporting MMIO, all previous versions
> uses Port IO for RX/TX notifications.
> 
> So, If I use VirtIO 0.9, Can I get the MMIO based notifications for RX/TX
> or is it supported only for Virt-IO 1.0 onwards?
> 

Although the virtio device will bind to the mmio address in some cases,
it does not use that. It uses i/o port access (see iopl) to activate
host.

Re: Regarding MMIO

[Venkateswara Rao Dokku]

Thanks for the response Stephen.

Are you referring to Virt-IO 0.9 in specific here in the response or for
any Virt-IO versions in general?

On Thu, Oct 1, 2015 at 8:12 PM, Stephen Hemminger <
stephen@networkplumber.org> wrote:

> On Thu, 1 Oct 2015 09:51:42 +0530
> Venkateswara Rao Dokku <dvrao.584@gmail.com> wrote:
>
> > Hi,
> >
> > If we go through the DPDK code it is observed that we are using MMIO for
> > Virt-IO devices. But in the Virt-IO specification, it is written that
> from
> > Virt-IO 1.0 onwards only they are supporting MMIO, all previous versions
> > uses Port IO for RX/TX notifications.
> >
> > So, If I use VirtIO 0.9, Can I get the MMIO based notifications for RX/TX
> > or is it supported only for Virt-IO 1.0 onwards?
> >
>
> Although the virtio device will bind to the mmio address in some cases,
> it does not use that. It uses i/o port access (see iopl) to activate
> host.
>



-- 
Thanks & Regards,
Venkateswara Rao Dokku.

Re: Regarding MMIO

[Xie, Huawei]

On 10/5/2015 12:41 PM, Venkateswara Rao Dokku wrote:
> Thanks for the response Stephen.
>
> Are you referring to Virt-IO 0.9 in specific here in the response or for
> any Virt-IO versions in general?
>
> On Thu, Oct 1, 2015 at 8:12 PM, Stephen Hemminger <
> stephen@networkplumber.org> wrote:
>
>> On Thu, 1 Oct 2015 09:51:42 +0530
>> Venkateswara Rao Dokku <dvrao.584@gmail.com> wrote:
>>
>>> Hi,
>>>
>>> If we go through the DPDK code it is observed that we are using MMIO for
>>> Virt-IO devices. But in the Virt-IO specification, it is written that
>> from
>>> Virt-IO 1.0 onwards only they are supporting MMIO, all previous versions
>>> uses Port IO for RX/TX notifications.
>>>
>>> So, If I use VirtIO 0.9, Can I get the MMIO based notifications for RX/TX
>>> or is it supported only for Virt-IO 1.0 onwards?
>>>
>> Although the virtio device will bind to the mmio address in some cases,
>> it does not use that. It uses i/o port access (see iopl) to activate
>> host.

Which is used depends on access time. Check the virtio 1.0 improvement
for mmio access.
http://events.linuxfoundation.org/sites/events/files/slides/misha2015-v1.pdf
Is there any special reason you want to use mmio based notification?

>
>