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

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

On Thu, May 12, 2016 at 05:52:54PM +0800, Jianbo Liu wrote:
> On 12 May 2016 at 16:57, Santosh Shukla
> <santosh.shukla@caviumnetworks.com> wrote:
> > 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.
> 
> We can't decide which kernel user will use.
>

yes, we can't decide kernel for user but we should be explicit to user on - what
works for dpdk/linux out-of-box vs what could work with use of out-of-tree
patch/RFC's.. example igb_uio.

> >
> > 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.
> 
> The patch is in the kernel maillist, and user google it.

there are feature specific rfc's in plenty in lkml/qemu mailing list,  and you
suggest- user to hunt for all those information. Is this how we;re officially
supporting igb_uio for arm64.. that let user to google?

> And isn't funny to ask someone to do something again and again (3
> times) in this thread?
>

I am asking becasue your in favour of keeping igb_uio for arm64 but not
agreeing to streamline (writing a note in dpdk doc for igb_uio for arm64 or
pointing to working tree).. so that user don;t need to grep or google for known
findings. 

I find discussion going in circle and nothing will conclude, So given up.
> >
> >> 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