mlx4 query in sriov mode

mlx4 query in sriov mode

[Bob Biloxi]

Hi All,


I really appreciate this wonderful community which has immensely
helped me broaden my knowledge and understanding.


I was going through the mlx4 sriov code, trying to understand the
communication between the VF driver and the PF driver.

I was having a few queries..hoping to get a better understanding.


As I understand, the commands are communicated between VF and PF
through a mechanism called communication channel. VF writes to
specific address in its BAR space, PF gets an event and then proceeds
ahead to read the command from its BAR space and then complete the
execution of it..


Now, my query is, lets say the VF driver is not yet present and only
the PF driver is there...

In this case, can we simulate a VF command write and get notified
through an event?

For eg. we write to some offset in the PF BAR space itself upon
completion of which, an event is generated because of the write? kind
of like loopback mechanism.


I searched through the code but couldn't find anywhere.

Can anyone please help me understand if this is possible? And if there
is any location in the code where i can find this?

Thanks a lot in advance!!


Best Regards,
Bob
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Re: mlx4 query in sriov mode

[Wei Yang]

On Thu, Aug 28, 2014 at 10:58:50PM +0530, Bob Biloxi wrote:
>Hi All,
>
>
>I really appreciate this wonderful community which has immensely
>helped me broaden my knowledge and understanding.
>
>
>I was going through the mlx4 sriov code, trying to understand the
>communication between the VF driver and the PF driver.
>
>I was having a few queries..hoping to get a better understanding.
>
>
>As I understand, the commands are communicated between VF and PF
>through a mechanism called communication channel. VF writes to
>specific address in its BAR space, PF gets an event and then proceeds
>ahead to read the command from its BAR space and then complete the
>execution of it..
>
>
>Now, my query is, lets say the VF driver is not yet present and only
>the PF driver is there...
>
>In this case, can we simulate a VF command write and get notified
>through an event?
>

Hi,

I am not that familiar with mlx4 driver. As you mentioned in previous, VF
communicate with PF by writing some word in BAR and PF gets it. If this is
true, I believe it would works.

>For eg. we write to some offset in the PF BAR space itself upon
>completion of which, an event is generated because of the write? kind
>of like loopback mechanism.
>
>
>I searched through the code but couldn't find anywhere.
>
>Can anyone please help me understand if this is possible? And if there
>is any location in the code where i can find this?

Where you fund the communication between PF and VF is by writing its BAR?

>
>Thanks a lot in advance!!
>
>
>Best Regards,
>Bob
>--
>To unsubscribe from this list: send the line "unsubscribe linux-pci" in
>the body of a message to majordomo@vger.kernel.org
>More majordomo info at  http://vger.kernel.org/majordomo-info.html

-- 
Richard Yang
Help you, Help me

Re: mlx4 query in sriov mode

[Bob Biloxi]

Hi,

> Where you fund the communication between PF and VF is by writing its BAR?
http://lxr.free-electrons.com/source/drivers/net/ethernet/mellanox/mlx4/cmd.c#L1964


Best Regards,
Bob

On Fri, Aug 29, 2014 at 9:51 AM, Wei Yang <weiyang@linux.vnet.ibm.com> wrote:
> On Thu, Aug 28, 2014 at 10:58:50PM +0530, Bob Biloxi wrote:
>>Hi All,
>>
>>
>>I really appreciate this wonderful community which has immensely
>>helped me broaden my knowledge and understanding.
>>
>>
>>I was going through the mlx4 sriov code, trying to understand the
>>communication between the VF driver and the PF driver.
>>
>>I was having a few queries..hoping to get a better understanding.
>>
>>
>>As I understand, the commands are communicated between VF and PF
>>through a mechanism called communication channel. VF writes to
>>specific address in its BAR space, PF gets an event and then proceeds
>>ahead to read the command from its BAR space and then complete the
>>execution of it..
>>
>>
>>Now, my query is, lets say the VF driver is not yet present and only
>>the PF driver is there...
>>
>>In this case, can we simulate a VF command write and get notified
>>through an event?
>>
>
> Hi,
>
> I am not that familiar with mlx4 driver. As you mentioned in previous, VF
> communicate with PF by writing some word in BAR and PF gets it. If this is
> true, I believe it would works.
>
>>For eg. we write to some offset in the PF BAR space itself upon
>>completion of which, an event is generated because of the write? kind
>>of like loopback mechanism.
>>
>>
>>I searched through the code but couldn't find anywhere.
>>
>>Can anyone please help me understand if this is possible? And if there
>>is any location in the code where i can find this?
>
> Where you fund the communication between PF and VF is by writing its BAR?
>
>>
>>Thanks a lot in advance!!
>>
>>
>>Best Regards,
>>Bob
>>--
>>To unsubscribe from this list: send the line "unsubscribe linux-pci" in
>>the body of a message to majordomo@vger.kernel.org
>>More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
> --
> Richard Yang
> Help you, Help me
>

Re: mlx4 query in sriov mode

[Bob Biloxi]

Hi,

Can anyone from Mellanox please help me understand this better? really
hoping for any pointers that will be helpful...

Specifically:

> Now, my query is, lets say the VF driver is not yet present and only
> the PF driver is there...
>
> In this case, can we simulate a VF command write and get notified
> through an event?
>
> For eg. we write to some offset in the PF BAR space itself upon
> completion of which, an event is generated because of the write? kind
> of like loopback mechanism.
>


Thanks so much,
Bob

On Thu, Aug 28, 2014 at 10:58 PM, Bob Biloxi <iambobbiloxi@gmail.com> wrote:
> Hi All,
>
>
> I really appreciate this wonderful community which has immensely
> helped me broaden my knowledge and understanding.
>
>
> I was going through the mlx4 sriov code, trying to understand the
> communication between the VF driver and the PF driver.
>
> I was having a few queries..hoping to get a better understanding.
>
>
> As I understand, the commands are communicated between VF and PF
> through a mechanism called communication channel. VF writes to
> specific address in its BAR space, PF gets an event and then proceeds
> ahead to read the command from its BAR space and then complete the
> execution of it..
>
>
> Now, my query is, lets say the VF driver is not yet present and only
> the PF driver is there...
>
> In this case, can we simulate a VF command write and get notified
> through an event?
>
> For eg. we write to some offset in the PF BAR space itself upon
> completion of which, an event is generated because of the write? kind
> of like loopback mechanism.
>
>
> I searched through the code but couldn't find anywhere.
>
> Can anyone please help me understand if this is possible? And if there
> is any location in the code where i can find this?
>
> Thanks a lot in advance!!
>
>
> Best Regards,
> Bob