Re: [dpdk-dev] [PATCH] bus/pci: fix IOVA as VA mode selection

[David Marchand <david.marchand@redhat.com>]

On Mon, Jul 8, 2019 at 4:25 PM <jerinj@marvell.com> wrote:

> From: Jerin Jacob <jerinj@marvell.com>
>
> Existing logic fails to select IOVA mode as VA
> if driver request to enable IOVA as VA.
>
> IOVA as VA has more strict requirement than other modes,
> so enabling positive logic for IOVA as VA selection.
>
> This patch also updates the default IOVA mode as PA
> for PCI devices as it has to deal with DMA engines unlike
> the virtual devices that may need only IOVA as DC.
>

We have three cases:
- driver/hw supports IOVA as PA only
- driver/hw supports IOVA as both VA and PA
- driver/hw supports IOVA as VA only

Looking at the header:
/** Device driver supports IOVA as VA */
#define RTE_PCI_DRV_IOVA_AS_VA 0X0040

It clearly states that the driver supports IOVA as VA, and not requires.
With only one flag, we can't decide on those three cases and we might want
to introduce a new flag for your usecase.

But, in any case, this is too short for -rc1.
I prefer to nak this patch for now.
You can still set --iova-mode=va and we can try to find a solution for -rc2.


-- 
David Marchand