On 7/1/2016 1:47 PM, Thomas Monjalon wrote: > 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. I will re-word.
> >> 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? request_mem_region() is a way for driver informing the rest of the kernel that memory region is used. And with CONFIG_IO_STRICT_DEVMEM=y, userspace also prevented to touch that ares. But for igb_uio, we explicitly want userspace to access that memory range. > Please could you give an example of what could happen? Technically device lost a protection of its memory region against any other driver, but I am not sure if this is real threat in practical life. Also this is same in uio_pci_generic, it doesn't reserve the memory. > > This patch fixes a problem with recent kernels (not mentioned above) > which offer the uio_pci_generic alternative. Will give kernel version information. > That's why I think we should fix it only if there is absolutely no > regression for older kernels. > Totally agreed, that is why I expressed my concern, let this patch hang around a little.
