2016-07-01 15:39, Ferruh Yigit: > On 7/1/2016 1:47 PM, Thomas Monjalon wrote: > >> 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.
OK thanks for the explanations. So we are not sure how this memory region can be stolen and we assume it won't. > > 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. It may be valuable to have in 16.07. I suggest to wait RC3 (mid-July) to integrate it. We will have a RC4 to test it.
