On Thu, Sep 9, 2021 at 8:00 AM Yuri Benditovich <yuri.benditov...@daynix.com> wrote: > > On Wed, Sep 8, 2021 at 6:45 AM Jason Wang <jasow...@redhat.com> wrote: > > > > On Tue, Sep 7, 2021 at 6:40 PM Yuri Benditovich > > <yuri.benditov...@daynix.com> wrote: > > > > > > 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. > > > > > > Hi Jason, > > > > > > Indeed I did not get the idea, can you please explain it in more > > > details (as detailed as possible to avoid future misunderstanding), > > > especially how exactly we can use the set-uid and what is the 'default' > > > helper. > > > We also would prefer to do everything from qemu but we do not see how > > > we can do that. > > > > > Some more questions to understand the idea better: > > Something like: > > > > 1) -netdev tap,rss_helper=/path/to/name > > So, on each editing of 'emulator' in the xml the helper path should > be set manually or be default?
It could done manually, or we can have a default path. > > > 2) having a sample/default helper implemented in Qemu > > Does it mean the default helper is the code in the qemu (without > running additional executable, like it does today) Yes. or this is qemu > itself with dedicated command line? > As far as I remember Daniel had strong objections of ever running qemu > with capabilities Qemu won't run with capabilities but the helper. > > > 3) we can introduce something special path like "default", then if > > -netdev tap,rss_helper="default" is specified, qemu will use the > > sample helper > > Probably this is not so important but the rss helper and rss in > general has no relation to netdev, much more they are related to > virtio-net So I think the reason for this is that we currently only support eBPF/RSS for tap. > > > > > So we have: > > 1) set set-uid for the helper > Who and when does set-uid to the helper binary? Only installer or > libvirt can do that, correct? Yes, it could be done the installer, or other system provision tools. > > > 2) libvirt may just choose to launch the default helper > All this discussion is to avoid launching the helper from libvirt, correct? Sorry, it's a typo. I meant, libvirt launch qemu, and then qemu will launch the helper. Thanks > > > > > > > > > Our main points (what should be addressed): > > > - qemu should be able to load ebpf and use the maps when it runs from > > > libvirt (without special caps) and standalone (with caps) > > > > This is solved by leaving the privileged operations to the helper with > > set-uid. > > > > > - it is possible that there are different qemu builds on the machine, > > > one of them might be installed, their ebpf's might be different and > > > the interface between qemu and ebpf (exact content of maps and number > > > of maps) > > > > We can use different helpers in this way. > > > > > - qemu configures the RSS dynamically according to the commands > > > provided by the guest > > > > Consider we decided to use mmap() based maps, this is not an issue. > > > > Or am I missing something? > > > > Thanks > > > > > > > > Thanks in advance > > > Yuri > > > > > > > > > > > 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 > > > > > > > > > >