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

[Santosh Shukla]

On Thu, Dec 17, 2015 at 3:32 PM, Santosh Shukla <sshukla at mvista.com> wrote:
> On Thu, Dec 17, 2015 at 3:31 PM, Santosh Shukla <sshukla at mvista.com> wrote:
>> 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.
>>
>>
> missed link;
>
> [1] http://dpdk.org/dev/patchwork/patch/9365/
>

IMO, it is worth keeping one special device file who could work across
archs like arm/arm64/powerpc and others, who could map iopci bar to
dpdk user-space. also this approach has no kernel version dependency
too. BTW; I did mentioned in second approach in to add /dev/ioport
interface in drivers/char/mem.c which could read more than byte in one
single operation, but that has kernel dependency. However that
approach too is arch agnostic.

Let me know!

>>>         --yliu