Re: [PATCH 4/5] ebpf_rss_helper: Added helper for eBPF RSS.

[Andrew Melnichenko]

Hi,

On Mon, Feb 20, 2023 at 11:54 AM Daniel P. Berrangé <berrange@redhat.com> wrote:
>
> On Sun, Feb 19, 2023 at 06:20:59PM +0200, Andrew Melnychenko wrote:
> > Helper program. Loads eBPF RSS program and maps and passes them through 
> > unix socket.
> > Libvirt may launch this helper and pass eBPF fds to qemu virtio-net.
> > Also, libbpf dependency for now is exclusively for Linux.
> > Libbpf is used for eBPF RSS steering, which is supported only by Linux TAP.
> > There is no reason yet to build eBPF loader and helper for non-Linux 
> > systems,
> > even if libbpf is present.
> >
> > Signed-off-by: Andrew Melnychenko <andrew@daynix.com>
> > ---
> >  ebpf/qemu-ebpf-rss-helper.c | 132 ++++++++++++++++++++++++++++++++++++
> >  meson.build                 |  37 ++++++----
> >  2 files changed, 156 insertions(+), 13 deletions(-)
> >  create mode 100644 ebpf/qemu-ebpf-rss-helper.c
> >
> > diff --git a/ebpf/qemu-ebpf-rss-helper.c b/ebpf/qemu-ebpf-rss-helper.c
> > new file mode 100644
> > index 0000000000..348d26bcdd
> > --- /dev/null
> > +++ b/ebpf/qemu-ebpf-rss-helper.c
> > @@ -0,0 +1,132 @@
> > +/*
> > + * eBPF RSS Helper
> > + *
> > + * Developed by Daynix Computing LTD (http://www.daynix.com)
> > + *
> > + * Authors:
> > + *  Andrew Melnychenko <andrew@daynix.com>
> > + *
> > + * This work is licensed under the terms of the GNU GPL, version 2.  See
> > + * the COPYING file in the top-level directory.
>
> Is there a reason for specifying GPL version 2 only ?
>
> Unless this has copied code from one of the existing GPLv2-only files
> in QEMU, the requirement (listed in LICENSE) is that new contributions
> will be GPLv2-or-later, except for a handful of sub-directories.
>

Yeah - I'll change it. Thank you.

>
>
> > + *
> > + * Description: This is helper program for libvirtd.
> > + *              It loads eBPF RSS program and passes fds through unix 
> > socket.
> > + *              Built by meson, target - 'qemu-ebpf-rss-helper'.
> > + */
> > +
> > +#include <stdio.h>
> > +#include <stdint.h>
> > +#include <stdlib.h>
> > +#include <stdbool.h>
> > +#include <getopt.h>
> > +#include <memory.h>
> > +#include <errno.h>
> > +#include <sys/socket.h>
> > +
> > +#include "ebpf_rss.h"
> > +
> > +#include "qemu-ebpf-rss-helper-stamp.h"
> > +
> > +void QEMU_EBPF_RSS_HELPER_STAMP(void) {}
> > +
> > +static int send_fds(int socket, int *fds, int n)
> > +{
> > +    struct msghdr msg = {};
> > +    struct cmsghdr *cmsg = NULL;
> > +    char buf[CMSG_SPACE(n * sizeof(int))];
> > +    char dummy_buffer = 0;
> > +    struct iovec io = { .iov_base = &dummy_buffer,
> > +                        .iov_len = sizeof(dummy_buffer) };
> > +
> > +    memset(buf, 0, sizeof(buf));
> > +
> > +    msg.msg_iov = &io;
> > +    msg.msg_iovlen = 1;
> > +    msg.msg_control = buf;
> > +    msg.msg_controllen = sizeof(buf);
> > +
> > +    cmsg = CMSG_FIRSTHDR(&msg);
> > +    cmsg->cmsg_level = SOL_SOCKET;
> > +    cmsg->cmsg_type = SCM_RIGHTS;
> > +    cmsg->cmsg_len = CMSG_LEN(n * sizeof(int));
> > +
> > +    memcpy(CMSG_DATA(cmsg), fds, n * sizeof(int));
> > +
> > +    return sendmsg(socket, &msg, 0);
> > +}
> > +
> > +static void print_help_and_exit(const char *prog, int exitcode)
> > +{
> > +    fprintf(stderr, "%s - load eBPF RSS program for qemu and pass eBPF fds"
> > +            " through unix socket.\n", prog);
> > +    fprintf(stderr, "\t--fd <num>, -f <num> - unix socket file descriptor"
> > +            " used to pass eBPF fds.\n");
> > +    fprintf(stderr, "\t--help, -h - this help.\n");
> > +    exit(exitcode);
> > +}
> > +
> > +int main(int argc, char **argv)
> > +{
> > +    char *fd_string = NULL;
> > +    int unix_fd = 0;
> > +    struct EBPFRSSContext ctx = {};
> > +    int fds[EBPF_RSS_MAX_FDS] = {};
> > +    int ret = -1;
> > +
> > +    for (;;) {
> > +        int c;
> > +        static struct option long_options[] = {
> > +                {"help",  no_argument, 0, 'h'},
> > +                {"fd",  required_argument, 0, 'f'},
> > +                {0, 0, 0, 0}
> > +        };
> > +        c = getopt_long(argc, argv, "hf:",
> > +                long_options, NULL);
> > +
> > +        if (c == -1) {
> > +            break;
> > +        }
> > +
> > +        switch (c) {
> > +        case 'f':
> > +            fd_string = optarg;
> > +            break;
> > +        case 'h':
> > +        default:
> > +            print_help_and_exit(argv[0],
> > +                    c == 'h' ? EXIT_SUCCESS : EXIT_FAILURE);
> > +        }
> > +    }
> > +
> > +    if (!fd_string) {
> > +        fprintf(stderr, "Unix file descriptor not present.\n");
> > +        print_help_and_exit(argv[0], EXIT_FAILURE);
> > +    }
> > +
> > +    unix_fd = atoi(fd_string);
> > +
> > +    if (!unix_fd) {
> > +        fprintf(stderr, "Unix file descriptor is invalid.\n");
> > +        return EXIT_FAILURE;
> > +    }
> > +
> > +    ebpf_rss_init(&ctx);
> > +    if (!ebpf_rss_load(&ctx)) {
> > +        fprintf(stderr, "Can't load ebpf.\n");
> > +        return EXIT_FAILURE;
> > +    }
> > +    fds[0] = ctx.program_fd;
> > +    fds[1] = ctx.map_configuration;
> > +    fds[2] = ctx.map_toeplitz_key;
> > +    fds[3] = ctx.map_indirections_table;
> > +
> > +    ret = send_fds(unix_fd, fds, EBPF_RSS_MAX_FDS);
> > +    if (ret < 0) {
> > +        fprintf(stderr, "Issue while sending fds: %s.\n", strerror(errno));
> > +    }
> > +
> > +    ebpf_rss_unload(&ctx);
> > +
> > +    return ret < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
> > +}
> > +
> > diff --git a/meson.build b/meson.build
> > index b409912aed..6e6e2f3e40 100644
> > --- a/meson.build
> > +++ b/meson.build
> > @@ -1632,19 +1632,22 @@ elif get_option('vduse_blk_export').disabled()
> >  endif
> >
> >  # libbpf
> > -libbpf = dependency('libbpf', required: get_option('bpf'), method: 
> > 'pkg-config')
> > -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')
> > +libbpf = not_found
> > +if targetos == 'linux'
> > +  libbpf = dependency('libbpf', required: get_option('bpf'), method: 
> > 'pkg-config')
> > +  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
> >  endif
> >
> > @@ -3646,6 +3649,14 @@ if have_tools
> >                 dependencies: [authz, crypto, io, qom, qemuutil,
> >                                libcap_ng, mpathpersist],
> >                 install: true)
> > +
> > +    if libbpf.found()
> > +        executable('qemu-ebpf-rss-helper', files(
> > +                   'ebpf/qemu-ebpf-rss-helper.c', 'ebpf/ebpf_rss.c'),
> > +                   dependencies: [qemuutil, libbpf, glib],
> > +                   install: true,
> > +                   install_dir: get_option('libexecdir'))
> > +    endif
> >    endif
> >
> >    if have_ivshmem
> > --
> > 2.39.1
> >
>
> With regards,
> Daniel
> --
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>