RE: [PATCH] net/hns3: support disable IOVA as PA mode

["Morten Brørup" <mb@smartsharesystems.com>]

> From: Thomas Monjalon [mailto:thomas@monjalon.net]
> Sent: Monday, 20 February 2023 08.45
> 
> 16/02/2023 09:36, Ruifeng Wang:
> > From: Chengwen Feng <fengchengwen@huawei.com>
> > > Subject: [PATCH] net/hns3: support disable IOVA as PA mode
> 
> Could we change the title to "support IOVA as VA" ?

The underlying problem is the meson configuration option name for this feature [1]:

option('enable_iova_as_pa', type: 'boolean', value: true, description:
       'Support for IOVA as physical address. Disabling removes the buf_iova field of mbuf.')

[1]: https://elixir.bootlin.com/dpdk/v22.11.1/source/meson_options.txt#L43

Formally, the patch provides the ability to set a boolean configuration value ("enable_iova_as_pa") to false, and thus the patch title is correct.

Nonetheless, I agree that the title suggested by Thomas is an improvement.


Going back to the root cause, I think the configuration option should be an enum instead of a boolean, e.g. "iova_mode" with values "iova_pa" and "iova_va".

It's somewhat similar to CPU endian macros. We have macros defining both Big Endian and Little Endian, not just one macro defining Big Endian or not.

@Bruce, would it be hard for you to change the IOVA configuration option from a boolean to a two-value enum?

Or - also considering the resulting #define's - would it be too difficult to keep a sufficient level of backwards/API compatibility?