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This reverts commit77b9c4a438, reversing changes made to4515ec4ad5:931420a2fc("selftests/net: Add netkit container tests")ab771c938d("selftests/net: Make NetDrvContEnv support queue leasing")6be87fbb27("selftests/net: Add env for container based tests")61d99ce3df("selftests/net: Add bpf skb forwarding program")920da36341("netkit: Add xsk support for af_xdp applications")eef51113f8("netkit: Add netkit notifier to check for unregistering devices")b5ef109d22("netkit: Implement rtnl_link_ops->alloc and ndo_queue_create")b5c3fa4a0b("netkit: Add single device mode for netkit")0073d2fd67("xsk: Proxy pool management for leased queues")1ecea95dd3("xsk: Extend xsk_rcv_check validation")804bf334d0("net: Proxy netdev_queue_get_dma_dev for leased queues")0caa9a8dde("net: Proxy net_mp_{open,close}_rxq for leased queues")ff8889ff91("net, ethtool: Disallow leased real rxqs to be resized")9e2103f361("net: Add lease info to queue-get response")31127dedde("net: Implement netdev_nl_queue_create_doit")a5546e18f7("net: Add queue-create operation") The series will conflict with io_uring work, and the code needs more polish. Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Why we want a copy of kernel headers in tools?
==============================================
There used to be no copies, with tools/ code using kernel headers
directly. From time to time tools/perf/ broke due to legitimate kernel
hacking. At some point Linus complained about such direct usage. Then we
adopted the current model.
The way these headers are used in perf are not restricted to just
including them to compile something.
There are sometimes used in scripts that convert defines into string
tables, etc, so some change may break one of these scripts, or new MSRs
may use some different #define pattern, etc.
E.g.:
$ ls -1 tools/perf/trace/beauty/*.sh | head -5
tools/perf/trace/beauty/arch_errno_names.sh
tools/perf/trace/beauty/drm_ioctl.sh
tools/perf/trace/beauty/fadvise.sh
tools/perf/trace/beauty/fsconfig.sh
tools/perf/trace/beauty/fsmount.sh
$
$ tools/perf/trace/beauty/fadvise.sh
static const char *fadvise_advices[] = {
[0] = "NORMAL",
[1] = "RANDOM",
[2] = "SEQUENTIAL",
[3] = "WILLNEED",
[4] = "DONTNEED",
[5] = "NOREUSE",
};
$
The tools/perf/check-headers.sh script, part of the tools/ build
process, points out changes in the original files.
So its important not to touch the copies in tools/ when doing changes in
the original kernel headers, that will be done later, when
check-headers.sh inform about the change to the perf tools hackers.
Another explanation from Ingo Molnar:
It's better than all the alternatives we tried so far:
- Symbolic links and direct #includes: this was the original approach but
was pushed back on from the kernel side, when tooling modified the
headers and broke them accidentally for kernel builds.
- Duplicate self-defined ABI headers like glibc: double the maintenance
burden, double the chance for mistakes, plus there's no tech-driven
notification mechanism to look at new kernel side changes.
What we are doing now is a third option:
- A software-enforced copy-on-write mechanism of kernel headers to
tooling, driven by non-fatal warnings on the tooling side build when
kernel headers get modified:
Warning: Kernel ABI header differences:
diff -u tools/include/uapi/drm/i915_drm.h include/uapi/drm/i915_drm.h
diff -u tools/include/uapi/linux/fs.h include/uapi/linux/fs.h
diff -u tools/include/uapi/linux/kvm.h include/uapi/linux/kvm.h
...
The tooling policy is to always pick up the kernel side headers as-is,
and integate them into the tooling build. The warnings above serve as a
notification to tooling maintainers that there's changes on the kernel
side.
We've been using this for many years now, and it might seem hacky, but
works surprisingly well.