[dpdk-dev] [PATCH] eal: map io resources for non x86 architectures

[Alex Williamson]

On Tue, 2015-12-29 at 16:17 +0530, Santosh Shukla wrote:
> On Tue, Dec 29, 2015 at 3:26 PM, Burakov, Anatoly
> <anatoly.burakov at intel.com> wrote:
> > Hi Santosh,
> > 
> > > On Fri, Dec 18, 2015 at 6:25 PM, Santosh Shukla <sshukla at mvista.c
> > > om>
> > > wrote:
> > > > On Fri, Dec 18, 2015 at 1:51 PM, Yuanhan Liu
> > > > <yuanhan.liu at linux.intel.com> wrote:
> > > > > On Fri, Dec 18, 2015 at 01:24:41PM +0530, Santosh Shukla
> > > > > wrote:
> > > > > > > > I guess we have done enough evaluation / investigation
> > > > > > > > that
> > > > > > > > suggest - so to map iopci region to userspace in arch
> > > > > > > > agnostic-way -
> > > > > > > > 
> > > > > > > > # either we need to modify kernel
> > > > > > > >                - Make sure all the non-x86 arch to
> > > > > > > > support
> > > > > > > > mapping for iopci region (i.e. pci_mmap_page_range). I
> > > > > > > > don;t
> > > > > > > > think its a correct approach though.
> > > > > > > >             or
> > > > > > > >                - include /dev/ioport char-mem device
> > > > > > > > file who
> > > > > > > > could do more than byte operation, Note that this
> > > > > > > > implementation
> > > > > > > > does not exist in kernel.  I could send an RFC to lkml.
> > > > > > > 
> > > > > > > Maybe you could propose the two to lkml, to get some
> > > > > > > feedbacks
> > > > > > > from those kernel/ARM gurus? Please cc me if you do so.
> > > > > > > 
> > > > > > 
> > > > > > The latter one I already shared old lkml thread, Pl.
> > > > > > revisit my v1
> > > > > > 0/6 patch [1] and in that refer [2].
> > > > > 
> > > > > Oops, sorry, a bit busy, that I didn't look at it carefully.
> > > > > My bad,
> > > > > anyway.
> > > > > 
> > > > > > Josh has already proposed to lkml but for some reason
> > > > > > thread didn't
> > > > > > went far. I can restart that discussion giving dpdk use-
> > > > > > case as an
> > > > > > example/ requirement.
> > > > > 
> > > > > I had a quick go through of the discussion. Both hpa and Arnd
> > > > > seem to
> > > > > be fine with the ioctl interface on /dev/port. Have you tried
> > > > > that?
> > > > > And if you want to restart it, ioctl might be a better option
> > > > > than
> > > > > /dev/ioport, judging from the discussion.
> > > > > 
> > > > 
> > > > I tried legacy patch and re-writing with ioctl-way; doing
> > > > changes in
> > > > dpdk port as well in kernel, had to test on quite other hw not
> > > > only
> > > > arm64 though! so it will take time for me, I am travelling
> > > > tomorrow so
> > > > bit delayed, We'll post patch to lkml and share dpdk-virtio
> > > > feedback
> > > > perhaps by Monday.
> > > > 
> > > 
> > > I posted a query about /dev/ioports approach in lkml thread [1],
> > > and Arnd
> > > suggested to use vfio framework but it looks like vfio too does
> > > not map
> > > ioresource_io region. Same communicated to Arnd and waiting for
> > > his reply.
> > > 
> > > In mean time I like to ask general question;
> > > - Has anyone tried vfio/non-iommu approach for virtio pmd driver?
> > > If not
> > > then Is there any plan? Someone planning to take up.
> > > [1] https://lkml.org/lkml/2015/12/23/145
> > 
> > I have submitted a patch to support no-iommu mode, but I'm not
> > aware of anyone trying VFIO-noiommu at all. That's probably
> > expected since it's Christmas/New Year in a lot of places, and
> > everyone is on a break.
> > 
> > That said, I'm not sure I completely understand what is it that
> > you're asking about. The code you're referring to (in vfio_pci.c,
> > line 854 as of kernel 4.3) is checking if a PCI BAR is available
> > for IO (hence checking if the IORESOURCE_MEM
> 
> 
> Thanks for reply! You comment might help to move this discuss to next
> level.
> 
> Look at kernel/resource.c, it exports two symbol ioport_resource and
> iomem_resource and sets appropriate flag type i.e.. IORESOURCE_IO and
> IORESOURCE_MEM. In virtio-net case; it creates both pci region i.e..
> _io bar and _mem bar. dpdk virtio pmd driver (<= 0.95 virtio spec)
> uses pci _io bar region for device initialization as virtio headers
> are locate at pci _io bar region. Since it uses pci _iobar region so
> likely it update pci_resource.[index].flag = IORESOURCE_IO.  and vfio
> mmap function wont handle ioresource_io (i guess). And that is why I
> asked same to lkml thread.
> 
> 
> bit is set). There isn't any "ioresource_mem" region as far as VFIO
> is
> concerned, there are only BARs, ROM, VGA and PCI
> config regions (linux/vfio.h, line 314 as of kernel 4.3). So if
> you're
> missing some PCI regions for VFIO to map, they would first need to be
> added to VFIO kernel implementation before they can be used by DPDK.
> That is, unless I'm misunderstanding something :)
> > 
> 
> Agree. As mentioned above, I guess ioresource_io pci bar
> implementation missing in vfio kernel? but before adding code support
> in kernel I would like to hear from experts example, You, Alex!
> (looping alex)

MMIO and I/O port space are simply regions as far as VFIO is concerned.
 The userspace API supports the concept of I/O port regions that can be
mmap'd by userspace, but the implementation does not since I/O port
regions cannot be mmap'd on x86.  Someone needs to propose some code
for vfio-pci to support it.  Thanks,

Alex