Re: [dpdk-dev] DPDK 21.11+ Windows Roadmap

[Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>]

2021-08-26 19:31 (UTC-0700), William Tu:
> Hi Dmitry,
> Thanks, I have one question.
> 
> On Thu, Aug 26, 2021 at 5:19 PM Dmitry Kozlyuk <dmitry.kozliuk@gmail.com> wrote:
> >
> > This roadmap has been discussed on Windows community calls Aug 5 and Aug 19
> > and it met no principal objections. It extends beyond the nearest release,
> > but it is useful to have a comprehensive backlog in one place.
> >
> > In 21.11 it looks realistic to have:
> >  
> [...]
> > 4. Miscellaneous
> >
> > 4.1. Refactor bus/pci (DmitryK)
> >
> >      Currently netuio maps BARs at PCI bus scan. This is against DPDK model
> >      and can break certain scenarios, like running apps with different sets of
> >      available PMDs. PCI bus driver code must be refactored.  
> 
> Can you elaborate more about the "against DPDK model" and the
> scenarios it might break?
> 
> I thought it's common that when a driver loads, it scans PCI configuration
> space, and mmap BARs. So I'm curious why it's an issue for DPDK.

Bus scan stage extracts information required to find the relevant PMD
(PCI ID) or to filter it using -a/-b options and to properly map it (kernel
driver, NUMA node, etc). Mapping BARs happens on the probe stage if required
by the PMD. Neither scan nor probe should keep device handles/files open
indefinitely if probing fails (on Windows it means the device cannot be
removed or bound to another driver), which is what scan does now.