On Mon, Sep 6, 2021 at 11:50 PM Andrew Melnichenko <and...@daynix.com> wrote: > > Hi, >> >> I think it's for back-compatibility. >> >> E.g current codes works without mmap(), and user will surprise that it >> wont' work after upgrading their qemu. > > Well, the current code would require additional capabilities with > "kernel.unprivileged_bpf_disabled=1", which may be possible on RedHat systems. > Technically we may have mmap test which will show that mmap for > BPF_MAP_TYPE_ARRAY works, but on the target system, we will know it only in > runtime. > If I'm not mistaken, mmap for BPF_MAP_TYPE_ARRAY was added before kernel 5.4 > and our bpf program requires kernel 5.8+.
Ok, if this is the case, please explain this in the commit log. Btw, any reason that 5.8 is required for our bpf program? Thanks > So, there are no reasons to add bpf() update map as a fallback for mmap(). > > On Wed, Sep 1, 2021 at 9:42 AM Jason Wang <jasow...@redhat.com> wrote: >> >> >> 在 2021/8/31 上午1:07, Yuri Benditovich 写道: >> > On Fri, Aug 20, 2021 at 6:41 AM Jason Wang <jasow...@redhat.com> wrote: >> >> >> >> 在 2021/7/13 下午11:37, Andrew Melnychenko 写道: >> >>> 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. >> >> >> >> I wonder if this can be done as helper for TAP/bridge. >> >> >> >> E.g it's the qemu to launch those helper with set-uid. >> >> >> >> Then libvirt won't even need to care about that? >> >> >> > There are pros and cons for such a solution with set-uid. >> > From my point of view one of the cons is that set-uid is efficient >> > only at install time so the coexistence of different qemu builds (and >> > different helpers for each one) is kind of problematic. >> > With the current solution this does not present any problem: the >> > developer can have several different builds, each one automatically >> > has its own helper and there is no conflict between these builds and >> > between these builds and installed qemu package. Changing the >> > 'emulator' in the libvirt profile automatically brings the proper >> > helper to work. >> >> >> I'm not sure I get you here. We can still have default/sample helper to >> make sure it works for different builds. >> >> If we can avoid the involvement of libvirt, that would be better. >> >> Thanks >> >> >> > >> >>> Also, libbpf dependency now 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 <and...@daynix.com> >> >>> --- >> >>> ebpf/qemu-ebpf-rss-helper.c | 130 ++++++++++++++++++++++++++++++++++++ >> >>> meson.build | 37 ++++++---- >> >>> 2 files changed, 154 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..fe68758f57 >> >>> --- /dev/null >> >>> +++ b/ebpf/qemu-ebpf-rss-helper.c >> >>> @@ -0,0 +1,130 @@ >> >>> +/* >> >>> + * eBPF RSS Helper >> >>> + * >> >>> + * Developed by Daynix Computing LTD (http://www.daynix.com) >> >>> + * >> >>> + * Authors: >> >>> + * Andrew Melnychenko <and...@daynix.com> >> >>> + * >> >>> + * This work is licensed under the terms of the GNU GPL, version 2. See >> >>> + * the COPYING file in the top-level directory. >> >>> + * >> >>> + * 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-helper-stamp.h" >> >>> + >> >>> +void QEMU_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; >> >>> + >> >>> + 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 257e51d91b..913aa1fee5 100644 >> >>> --- a/meson.build >> >>> +++ b/meson.build >> >>> @@ -1033,19 +1033,22 @@ if not get_option('fuse_lseek').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); >> >> >> >> Do we need to test whether the bpf can do mmap() here? >> >> >> >> Thanks >> >> >> >> >> >>> + 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 >> >>> >> >>> @@ -2423,6 +2426,14 @@ 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 'CONFIG_IVSHMEM' in config_host >>