[dpdk-dev] [PATCH] igb_uio: fix mmap failure

[Thomas Monjalon]

Thank you Ferruh for taking care of igb_uio.

2016-07-01 12:35, Ferruh Yigit:
> With kernels enabled CONFIG_IO_STRICT_DEVMEM option mmap the iomem area
> to userspace fails:

Maybe some words are missing.
Please check punctuation of the whole commit message to make it easier
to understand.

> EAL: pci_map_resource():
>          cannot mmap(39, 0x7f1c51800000, 0x100000, 0x0):
>          Invalid argument (0xffffffffffffffff)
> 
> As a workaround igb_uio can stop reserving PCI memory resources, from
> kernel point of view io-memory region looks like idle and mmap works
> again.
> 
> With this update device io-memory range is not protected against any
> other kernel driver claim ownership on those resources, which shouldn't
> be a problem for dpdk usage module.

Why it should not be a problem?
Please could you give an example of what could happen?

This patch fixes a problem with recent kernels (not mentioned above)
which offer the uio_pci_generic alternative.
That's why I think we should fix it only if there is absolutely no
regression for older kernels.