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

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

On Thu, May 12, 2016 at 01:54:13PM +0800, Jianbo Liu wrote:
> On 12 May 2016 at 13:06, Santosh Shukla
> <santosh.shukla@caviumnetworks.com> wrote:
> > 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
> 
> Can you read carefully about the guide at
> http://dpdk.org/doc/guides/linux_gsg/build_dpdk.html? It says to use
> uio_pci_generic, igb_uio or vfio-pci.

*** applicable and works for x86 only, not for arm64: because pci mmap support
not present for arm64, in that case we should update the doc.

> Could it be possible that the user in that thread has already read and
> tried them all and found that he can't enable vifo with his kernel,
> and igb_uio is the easy way for him and asked for help from community?
> If so, we have no choice but keeping igb_uio enabled.

By then vfionoiommu support was wip progress in dpdk/linux. but now it merged
and it works. So no need to retain igb_uio in base config for which to work -
user need to use mmap patch at linux side.

Or can you maintain out-of-tree pci mmap patch/ kerne source and make it
explicit somewhere in dpdk build doc that - if user want igb_uio way then
use kernel/mmap patch from x location.

> He use lsmod to show us the modules, most likely he know vifo-pci.
> 
> Below are the details on modules, hugepages and device binding.
> root at arm64:~# lsmod
> Module                  Size  Used by
> rte_kni               292795  0
> igb_uio                 4338  0
> ixgbe                 184456  0