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Re: [PATCH v6 0/7] eBPF RSS support for virtio-net

From: Andrew Melnichenko
Subject: Re: [PATCH v6 0/7] eBPF RSS support for virtio-net
Date: Tue, 27 Apr 2021 13:47:38 +0300
Hi,
I've checked the issue. Apparently, libbpf can't work with a skeleton on Debian.
Version check would not help - versioning differs at different distros.
I've added a small check:

diff --git a/meson.build b/meson.build
index ca551dd15d..4a51a25643 100644
--- a/meson.build
+++ b/meson.build
@@ -1018,6 +1018,20 @@ endif
 
 # libbpf
 libbpf = dependency('libbpf', required: get_option('bpf'))
+if libbpf.found() and not cc.links('''
+   #include <bpf/libbpf.h>
+   int main(void)
+   {
+     bpf_object__destroy_skeleton(NULL);
+     return 0;
+   }''', dependencies: libbpf)
+  libbpf = not_found
+  if get_option('bpf').enabled()
+    error('libbpf skeleton test failed')
+  else
+    warning('libbpf skeleton test failed, disabling')
+  endif
+endif
 
 if get_option('cfi')
   cfi_flags=[]

Is it possible to prepare an additional patch or should I prepare new eBPFv7 patches?


On Sun, Apr 25, 2021 at 6:32 AM Jason Wang <jasowang@redhat.com> wrote:

在 2021/4/12 下午4:25, Andrew Melnychenko 写道:
> This set of patches introduces the usage of eBPF for packet steering
> and RSS hash calculation:
> * RSS(Receive Side Scaling) is used to distribute network packets to
> guest virtqueues by calculating packet hash
> * Additionally adding support for the usage of RSS with vhost
>
> The eBPF works on kernels 5.8+
> On earlier kerneld it fails to load and the RSS feature is reported
> only without vhost and implemented in 'in-qemu' software.
>
> Implementation notes:
> Linux TAP TUNSETSTEERINGEBPF ioctl was used to set the eBPF program.
> Added libbpf dependency and eBPF support.
> The eBPF program is part of the qemu and presented as an array
> of BPF ELF file data. The eBPF array file initially generated by bpftool.
> The compilation of eBPF is not part of QEMU build and can be done
> using provided Makefile.ebpf.
> Added changes to virtio-net and vhost, primary eBPF RSS is used.
> 'in-qemu' RSS used in the case of hash population and as a fallback option.
> For vhost, the hash population feature is not reported to the guest.
>
> Please also see the documentation in PATCH 6/7.
>
> Known issues:
> * hash population not supported by eBPF RSS: 'in-qemu' RSS used
> as a fallback, also, hash population feature is not reported to guests
> with vhost.
> * IPv6 extensions still in progress.


Want to merge but it fails to build on Debian 10.9:

dpkg -l | grep libbpf
ii  libbpf-dev:amd64              4.19.181-1 amd64        eBPF helper
library (development files)
ii  libbpf4.19:amd64              4.19.181-1 amd64        eBPF helper
library (shared library)

I configure use --enable-bpf --target-list=x86_64-softmmu, and I get:

[3/1375] Compiling C object libcommon.fa.p/ebpf_ebpf_rss.c.o
FAILED: libcommon.fa.p/ebpf_ebpf_rss.c.o
cc -Ilibcommon.fa.p -I. -I.. -I../slirp -I../slirp/src -I../dtc/libfdt
-I../capstone/include/capstone -Iqapi -Itrace -Iui -Iui/shader
-I/usr/include/libmount -I/usr/include/blkid -I/usr/include/uuid
-I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include
-I/usr/include/gio-unix-2.0 -I/usr/include/pixman-1
-fdiagnostics-color=auto -pipe -Wall -Winvalid-pch -Werror -std=gnu99
-O2 -g -isystem /home/devel/git/qemu/linux-headers -isystem
linux-headers -iquote . -iquote /home/devel/git/qemu -iquote
/home/devel/git/qemu/include -iquote /home/devel/git/qemu/disas/libvixl
-iquote /home/devel/git/qemu/tcg/i386 -iquote
/home/devel/git/qemu/accel/tcg -pthread -U_FORTIFY_SOURCE
-D_FORTIFY_SOURCE=2 -m64 -mcx16 -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64
-D_LARGEFILE_SOURCE -Wstrict-prototypes -Wredundant-decls -Wundef
-Wwrite-strings -Wmissing-prototypes -fno-strict-aliasing -fno-common
-fwrapv -Wold-style-declaration -Wold-style-definition -Wtype-limits
-Wformat-security -Wformat-y2k -Winit-self -Wignored-qualifiers
-Wempty-body -Wnested-externs -Wendif-labels -Wexpansion-to-defined
-Wimplicit-fallthrough=2 -Wno-missing-include-dirs
-Wno-shift-negative-value -Wno-psabi -fstack-protector-strong -fPIC -MD
-MQ libcommon.fa.p/ebpf_ebpf_rss.c.o -MF
libcommon.fa.p/ebpf_ebpf_rss.c.o.d -o libcommon.fa.p/ebpf_ebpf_rss.c.o
-c ../ebpf/ebpf_rss.c
In file included from ../ebpf/ebpf_rss.c:23:
/home/devel/git/qemu/ebpf/rss.bpf.skeleton.h: In function
‘rss_bpf__destroy’:
/home/devel/git/qemu/ebpf/rss.bpf.skeleton.h:32:3: error: implicit
declaration of function ‘bpf_object__destroy_skeleton’; did you mean
‘bpf_object__kversion’? [-Werror=implicit-function-declaration]
    bpf_object__destroy_skeleton(obj->skeleton);
    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
    bpf_object__kversion
/home/devel/git/qemu/ebpf/rss.bpf.skeleton.h:32:3: error: nested extern
declaration of ‘bpf_object__destroy_skeleton’ [-Werror=nested-externs]
/home/devel/git/qemu/ebpf/rss.bpf.skeleton.h: At top level:
/home/devel/git/qemu/ebpf/rss.bpf.skeleton.h:40:33: error: ‘struct
bpf_object_open_opts’ declared inside parameter list will not be visible
outside of this definition or declaration [-Werror]
  rss_bpf__open_opts(const struct bpf_object_open_opts *opts)
                                  ^~~~~~~~~~~~~~~~~~~~
/home/devel/git/qemu/ebpf/rss.bpf.skeleton.h: In function
‘rss_bpf__open_opts’:
/home/devel/git/qemu/ebpf/rss.bpf.skeleton.h:49:6: error: implicit
declaration of function ‘bpf_object__open_skeleton’; did you mean
‘bpf_object__open_buffer’? [-Werror=implicit-function-declaration]
   if (bpf_object__open_skeleton(obj->skeleton, opts))
       ^~~~~~~~~~~~~~~~~~~~~~~~~
       bpf_object__open_buffer
/home/devel/git/qemu/ebpf/rss.bpf.skeleton.h:49:6: error: nested extern
declaration of ‘bpf_object__open_skeleton’ [-Werror=nested-externs]
/home/devel/git/qemu/ebpf/rss.bpf.skeleton.h: In function ‘rss_bpf__load’:
/home/devel/git/qemu/ebpf/rss.bpf.skeleton.h:67:9: error: implicit
declaration of function ‘bpf_object__load_skeleton’; did you mean
‘bpf_object__load’? [-Werror=implicit-function-declaration]
   return bpf_object__load_skeleton(obj->skeleton);
          ^~~~~~~~~~~~~~~~~~~~~~~~~
          bpf_object__load
/home/devel/git/qemu/ebpf/rss.bpf.skeleton.h:67:9: error: nested extern
declaration of ‘bpf_object__load_skeleton’ [-Werror=nested-externs]
/home/devel/git/qemu/ebpf/rss.bpf.skeleton.h: In function ‘rss_bpf__attach’:
/home/devel/git/qemu/ebpf/rss.bpf.skeleton.h:88:9: error: implicit
declaration of function ‘bpf_object__attach_skeleton’; did you mean
‘bpf_object__for_each_safe’? [-Werror=implicit-function-declaration]
   return bpf_object__attach_skeleton(obj->skeleton);
          ^~~~~~~~~~~~~~~~~~~~~~~~~~~
          bpf_object__for_each_safe
/home/devel/git/qemu/ebpf/rss.bpf.skeleton.h:88:9: error: nested extern
declaration of ‘bpf_object__attach_skeleton’ [-Werror=nested-externs]
/home/devel/git/qemu/ebpf/rss.bpf.skeleton.h: In function ‘rss_bpf__detach’:
/home/devel/git/qemu/ebpf/rss.bpf.skeleton.h:94:9: error: implicit
declaration of function ‘bpf_object__detach_skeleton’; did you mean
‘bpf_object__for_each_safe’? [-Werror=implicit-function-declaration]
   return bpf_object__detach_skeleton(obj->skeleton);
          ^~~~~~~~~~~~~~~~~~~~~~~~~~~
          bpf_object__for_each_safe
/home/devel/git/qemu/ebpf/rss.bpf.skeleton.h:94:9: error: nested extern
declaration of ‘bpf_object__detach_skeleton’ [-Werror=nested-externs]
/home/devel/git/qemu/ebpf/rss.bpf.skeleton.h:94:9: error: ‘return’ with
a value, in function returning void [-Werror]
   return bpf_object__detach_skeleton(obj->skeleton);
          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/devel/git/qemu/ebpf/rss.bpf.skeleton.h:92:1: note: declared here
  rss_bpf__detach(struct rss_bpf *obj)
  ^~~~~~~~~~~~~~~
/home/devel/git/qemu/ebpf/rss.bpf.skeleton.h: In function
‘rss_bpf__create_skeleton’:
/home/devel/git/qemu/ebpf/rss.bpf.skeleton.h:102:53: error:
dereferencing pointer to incomplete type ‘struct bpf_object_skeleton’
   s = (struct bpf_object_skeleton *)calloc(1, sizeof(*s));
                                                      ^~
cc1: all warnings being treated as errors

Thanks


>
> Changes since v1:
> * using libbpf instead of direct 'bpf' system call.
> * added libbpf dependency to the configure/meson scripts.
> * changed python script for eBPF .h file generation.
> * changed eBPF program - reading L3 proto from ethernet frame.
> * added TUNSETSTEERINGEBPF define for TUN.
> * changed the maintainer's info.
> * added license headers.
> * refactored code.
>
> Changes since v2:
> * using bpftool for eBPF skeleton generation.
> * ebpf_rss is refactored to use skeleton generated by bpftool.
> * added/adjasted license in comment sections and in eBPF file.
> * rss.bpf.c and Makefile.ebpf moved to the tool/ebpf folder.
> * virtio-net eBPF rss refactored. Now eBPF initialized during realize().
>
> Changes since v3:
> * rebased to last master.
> * fixed issue with failed build without libbpf.
> * fixed ebpf loading without rss option.
> * refactored labels in ebpf_rss.c
>
> Changes since v4:
> * refactored configure/meson script.
> * added checks for load_bytes in ebpf.
> * documentation added to the index.
> * refactored Makefile and rss.bpf.c.
> * rebased to last master.
>
> Changes since v5:
> * fixed issue with dstopt parsing in the eBPF program.
> * added fragment packet parsing to skip L4.
>
> Andrew (7):
>    net/tap: Added TUNSETSTEERINGEBPF code.
>    net: Added SetSteeringEBPF method for NetClientState.
>    ebpf: Added eBPF RSS program.
>    ebpf: Added eBPF RSS loader.
>    virtio-net: Added eBPF RSS to virtio-net.
>    docs: Added eBPF documentation.
>    MAINTAINERS: Added eBPF maintainers information.
>
>   MAINTAINERS                    |   8 +
>   configure                      |   8 +-
>   docs/devel/ebpf_rss.rst        | 125 ++++++++
>   docs/devel/index.rst           |   1 +
>   ebpf/ebpf_rss-stub.c           |  40 +++
>   ebpf/ebpf_rss.c                | 165 ++++++++++
>   ebpf/ebpf_rss.h                |  44 +++
>   ebpf/meson.build               |   1 +
>   ebpf/rss.bpf.skeleton.h        | 431 +++++++++++++++++++++++++
>   ebpf/trace-events              |   4 +
>   ebpf/trace.h                   |   2 +
>   hw/net/vhost_net.c             |   3 +
>   hw/net/virtio-net.c            | 115 ++++++-
>   include/hw/virtio/virtio-net.h |   4 +
>   include/net/net.h              |   2 +
>   meson.build                    |   9 +
>   meson_options.txt              |   2 +
>   net/tap-bsd.c                  |   5 +
>   net/tap-linux.c                |  13 +
>   net/tap-linux.h                |   1 +
>   net/tap-solaris.c              |   5 +
>   net/tap-stub.c                 |   5 +
>   net/tap.c                      |   9 +
>   net/tap_int.h                  |   1 +
>   net/vhost-vdpa.c               |   2 +
>   tools/ebpf/Makefile.ebpf       |  22 ++
>   tools/ebpf/rss.bpf.c           | 569 +++++++++++++++++++++++++++++++++
>   27 files changed, 1592 insertions(+), 4 deletions(-)
>   create mode 100644 docs/devel/ebpf_rss.rst
>   create mode 100644 ebpf/ebpf_rss-stub.c
>   create mode 100644 ebpf/ebpf_rss.c
>   create mode 100644 ebpf/ebpf_rss.h
>   create mode 100644 ebpf/meson.build
>   create mode 100644 ebpf/rss.bpf.skeleton.h
>   create mode 100644 ebpf/trace-events
>   create mode 100644 ebpf/trace.h
>   create mode 100755 tools/ebpf/Makefile.ebpf
>   create mode 100644 tools/ebpf/rss.bpf.c
>

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