Re: [dpdk-dev] [PATCHv3 1/2] config/armv8a: disable igb_uio

[Santosh Shukla <santosh.shukla@caviumnetworks.com>]

On Thu, May 12, 2016 at 11:42:26AM +0800, Jianbo Liu wrote:
> On 12 May 2016 at 11:17, Santosh Shukla
> <santosh.shukla@caviumnetworks.com> wrote:
> > On Thu, May 12, 2016 at 10:01:05AM +0800, Jianbo Liu wrote:
> >> On 12 May 2016 at 02:25, Stephen Hemminger <stephen@networkplumber.org> wrote:
> >> > On Wed, 11 May 2016 22:32:16 +0530
> >> > Jerin Jacob <jerin.jacob@caviumnetworks.com> wrote:
> >> >
> >> >> On Wed, May 11, 2016 at 08:22:59AM -0700, Stephen Hemminger wrote:
> >> >> > On Wed, 11 May 2016 19:17:58 +0530
> >> >> > Hemant Agrawal <hemant.agrawal@nxp.com> wrote:
> >> >> >
> >> >> > > IGB_UIO not supported for arm64 arch in kernel so disable.
> >> >> > >
> >> >> > > Signed-off-by: Hemant Agrawal <hemant.agrawal@nxp.com>
> >> >> > > Reviewed-by: Santosh Shukla <santosh.shukla@caviumnetworks.com>
> >> >> >
> >> >> > Really, I have use IGB_UIO on ARM64
> >> >>
> >> >> May I know what is the technical use case for igb_uio on arm64
> >> >> which cannot be addressed through vfio or vfioionommu.
> >> >
> >> > I was running on older kernel which did not support vfioionommu mode.
> >>
> >> As I said, most of DPDK developers are not kernel developers. They may
> >> have their own kernel tree, and couldn't like to upgrade to latest
> >> kernel.
> >> They can choose to use or not use igb_uio when binding the driver. But
> >> blindly disabling it in the base config seems unreasonable.
> >
> > if user keeping his own kernel so they could also keep IGB_UIO=y in their local
> Most likely they don't have local dpdk tree. They write their own
> applications, complie and link to dpdk lib, then done.
> 
> > dpdk tree. Why are you imposing user-x custome depedancy on upstream dpdk base
> Customer requiremnts is important. I want they can choose the way they like.
>

so you choose to keep igb_uio option, provided arch doesn't support?
new user did reported issues with igb_uio for arm64, refer this thread [1], as
well hemanth too faced issues. we want to avoid that. 

If customer maintaing out-of-tree kernel then he can also switch to vfio-way.
isn;t it?

> > config. Is it not enough for explanation that - Base config ie.. armv8 doesn;t
> > support pci mmap, so igb_uio is n/a. New user wont able to build/run dpdk/arm64
> > in igb_uio-way, He'll prefer to use upstream stuff. I think, you are not making
> You are wrong, he can build dpdk. If he like to use upstream without
> patching, he can use vfio.

I disagree, we want to avoid [1] for new user.

> But you can't ignore the need from old user which is more comfortable
> with older kernel.
> 
arm/arm64 dpdk support recently added and I am guessing, most likely customer
using near latest kernel, switching to vfio won't be so difficult.

Or can you take up responsibility of upstreaming pci mmap patch, then we don't
need this patch.

[1] http://dpdk.org/ml/archives/dev/2016-January/031313.html
> > sense.
> >