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

[Santosh Shukla]

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.

>>
>> And for the former one, I'll have to check with linux-arm why iopci
>> region not mappable. By grepping kernel source all i could see two
>> commit - latest one is 415ae101 and older one 1da177e. Both has
>> nothing to explain why
>> if (mmap_state == pci_mmap_io)
>>       return -EINVAL;
>>
>> Setting pci io region to -EINVAL, should have fundamental reason for
>> sure. But we'll have to check, for that I could post as a query rather
>> a patch to lkml.
>
> No idea, such check should have been there in the very beginning
> for some reason. And here is a quote from Arnd:
>
>     Only powerpc, microblaze, alpha, sparc and xtensa allow
>     users to mmap I/O space, even though a lot of others could.
>
>>
>> Note that dpdk already has out-of-tree implementation for
>> dom0/xen-case too, it creates special device file which maps pci
>> resources. so keep one more igb_uio char device so to map iopci region
>> wont hurt much though!
>
> Xen is not a good example here; I'm even not sure it still works
> or not :)
>
>         --yliu
>> [1] http://permalink.gmane.org/gmane.comp.networking.dpdk.devel/29531
>>
>> >         --yliu
>> >>
>> >> OR keep device file in user space (current approach)
>> >> Right now Virtio-for-arm patches are blocked on this, let me know if
>> >> someone has better approach/thought in mind.
>> >>
>> >> Thanks.
>> >>
>> >> > Then we can try a pci_mmap solution or, as you suggest, an interface in
>> >> > drivers/char/mem.c
>> >> >