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

[Santosh Shukla]

On Thu, Dec 17, 2015 at 3:08 PM, Yuanhan Liu
<yuanhan.liu at linux.intel.com> wrote:
> On Wed, Dec 16, 2015 at 07:21:55PM +0530, Santosh Shukla wrote:
>> On Wed, Dec 16, 2015 at 6:18 PM, Yuanhan Liu
>> <yuanhan.liu at linux.intel.com> wrote:
>> > On Wed, Dec 16, 2015 at 01:31:04PM +0100, David Marchand wrote:
>> >> x86 requires a special set of instructions to access ioports, but other
>> >> architectures let you remap io resources.
>> >> So let eal remap io resources by accepting IORESOURCE_IO flag for
>> >> architectures other than x86.
>> >
>> > One question: this patch could be a replacement of the igbuio_iomap patch
>> > from Santosh? If so, I like it: It's more elegant.
>> >
>> >         --yliu
>> >
>>
>> I did tried similar in past but not in parse_sysfs (such that
>> mem.resource_addr to accept IO_RESOURCE_IO types) and observed that
>> pci_map_resource not able to map address hence segfault at tespmd
>> initialization.
>>
>> i was getting these:
>> EAL: pci_map_resource(): cannot mmap(19, 0x7fa5c00000, 0x20, 0x0):
>> Invalid argument (0xffffffffffffffff)
>
> That's because ARM (at least the kernel) doesn't allow an IO map:
>
> arch/arm/kernel/bios32.c
> ------------------------
> 618 int pci_mmap_page_range(struct pci_dev *dev, struct vm_area_struct *vma,
> 619                         enum pci_mmap_state mmap_state, int write_combine)
> 620 {
> 621         if (mmap_state == pci_mmap_io)
> 622                 return -EINVAL;
>
> And with a quick glimpse of powerpc, I see no such limitation. Hence,
> this peice of code may work only on Powerpc platform (and maybe a few
> others we don't care).
>
> So, apparently, this will not work for ARM.
>

Right and I did shared detailed explanation on why it wont work on
this link [1], infact this patch shouldn;t work for mips too.

As I mentioned earlier I did tried similar approach and so to get
everything working like iomem is currently in dpdk; we need to add
something like pci_remap_iospace --> ioremap_page_range() but this api
not really pci_mmap_page_range types. user need to write more code on
top so to use this api efficiently, also this api looks like meant to
use by arch file only in kernel space.


>         --yliu