virtq configuration over PCI

[Lior Narkis <liorn@mellanox.com>]

Hi All,
I am trying to figure out how the queue_select mechanism works.
It seems that there is an assumption that the device can react to the pcie write of the queue index to queue_select, 
before other pcie transactions that come after are being served.
So for example, reading the queue_size after writing to queue_select.

I would like to understand if I captured it right, and if so, understand how it is guaranteed today with a SW implementation of a device.

Having an HW implementation in mind, I believe this mechanism limits some possible implementations, and it is not robust for adding/changing new queue properties, which will require a new field on the PCIe BAR.

I believe a cleaner way will be to have a queue for device management.
The parameters of how to access this queue should be R/W on the PCIe BAR, but there is only one such queue so no need for the select.
In this queue the work is a command to the device. e.g create_virtq

Kind Regards,
Lior Narkis