68d676a089
Stopping offload completely if replace of program failed dates back to days of transparent offload. Back then we wanted to silently fall back to the in-driver processing. Today we mark programs for offload when they are loaded into the kernel, so the transparent offload is no longer a reality. Flags check in the driver will only allow replace of a driver program with another driver program or an offload program with another offload program. When driver program is replaced stopping offload is a no-op, because driver program isn't offloaded. When replacing offloaded program if the offload fails the entire operation will fail all the way back to user space and we should continue using the old program. IOW when replacing a driver program stopping offload is unnecessary and when replacing offloaded program - it's a bug, old program should continue to run. In practice this bug would mean that if offload operation was to fail (either due to FW communication error, kernel OOM or new program being offloaded but for a different netdev) driver would continue reporting that previous XDP program is offloaded but in fact no program will be loaded in hardware. The failure is fairly unlikely (found by inspection, when working on the code) but it's unpleasant. Backport note: even though the bug was introduced in commitcafa92ac25("nfp: bpf: add support for XDP_FLAGS_HW_MODE"), this fix depends on commit441a33031f("net: xdp: don't allow device-bound programs in driver mode"), so this fix is sufficient only in v4.15 or newer. Kernels v4.13.x and v4.14.x do need to stop offload if it was transparent/opportunistic, i.e. if XDP_FLAGS_HW_MODE was not set on running program. Fixes:cafa92ac25("nfp: bpf: add support for XDP_FLAGS_HW_MODE") Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com> Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com> Acked-by: Song Liu <songliubraving@fb.com> Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.