Message ID | 20201102185115.7425-7-andrew@daynix.com |
---|---|
State | New |
Headers | show |
Series | [RFC,1/6] net: Added SetSteeringEBPF method for NetClientState. | expand |
On 2020/11/3 上午2:51, Andrew Melnychenko wrote: > From: Andrew <andrew@daynix.com> > > Also, added maintainers information. > > Signed-off-by: Yuri Benditovich <yuri.benditovich@daynix.com> > Signed-off-by: Andrew Melnychenko <andrew@daynix.com> > --- > MAINTAINERS | 6 +++ > docs/ebpf.rst | 29 +++++++++++ > docs/ebpf_rss.rst | 129 ++++++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 164 insertions(+) > create mode 100644 docs/ebpf.rst > create mode 100644 docs/ebpf_rss.rst > > diff --git a/MAINTAINERS b/MAINTAINERS > index 2c22bbca5a..464b3f3c95 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -3111,6 +3111,12 @@ S: Maintained > F: hw/semihosting/ > F: include/hw/semihosting/ > > +EBPF: > +M: Andrew Melnychenko <andrew@daynix.com> > +M: Yuri Benditovich <yuri.benditovich@daynix.com> > +S: Maintained > +F: ebpf/* > + > Build and test automation > ------------------------- > Build and test automation > diff --git a/docs/ebpf.rst b/docs/ebpf.rst > new file mode 100644 > index 0000000000..e45d085432 > --- /dev/null > +++ b/docs/ebpf.rst > @@ -0,0 +1,29 @@ > +=========================== > +eBPF qemu support > +=========================== > + > +eBPF support (CONFIG_EBPF) is enabled automatically by 'configure' script > +if 'bpf' system call is available. > +To disable eBPF support use './configure --disable-bpf' > + > +Basic eBPF functionality is located in ebpf/ebpf.c and ebpf/ebpf.h. > +There are basic functions to load the eBPF program into the kernel. > +Mostly, functions name are self-explanatory: > + > +- `bpf_create_map()`, `bpf_lookup_element()`, `bpf_update_element()`, `bpf_delete_element()` - manages eBPF maps. On error, a basic error message would be reported and returned -1. On success, 0 would be returned(`bpf_create_map()` returns map's file descriptor). > +- `bpf_prog_load()` - load the program. The program has to have proper map file descriptors if there are used. On error - the log eBPF would be reported. On success, the program file descriptor returned. > +- `bpf_fixup_mapfd()` - would place map file descriptor into the program according to 'relocate array' of 'struct fixup_mapfd_t'. The function would return how many instructions were 'fixed' aka how many relocations was occurred. > + > +Simplified workflow would look like this: > + > +.. code:: C > + > + int map1 = bpf_create_map(...); > + int map2 = bpf_create_map(...); > + > + bpf_fixup_mapfd(<fixup table>, ARRAY_SIZE(<fixup table>), <instructions pointer>, ARRAY_SIZE(<instructions pointer>), <map1 name>, map1); > + bpf_fixup_mapfd(<fixup table>, ARRAY_SIZE(<fixup table>), <instructions pointer>, ARRAY_SIZE(<instructions pointer>), <map2 name>, map2); > + > + int prog = bpf_prog_load(<program type>, <instructions pointer>, ARRAY_SIZE(<instructions pointer>), "GPL"); > + > +See the bpf(2) for details. > diff --git a/docs/ebpf_rss.rst b/docs/ebpf_rss.rst > new file mode 100644 > index 0000000000..96fee391b8 > --- /dev/null > +++ b/docs/ebpf_rss.rst > @@ -0,0 +1,129 @@ > +=========================== > +eBPF RSS virtio-net support > +=========================== > + > +RSS(Receive Side Scaling) is used to distribute network packets to guest virtqueues > +by calculating packet hash. Usually every queue is processed then by a specific guest CPU core. > + > +For now there are 2 RSS implementations in qemu: > +- 'software' RSS (functions if qemu receives network packets, i.e. vhost=off) > +- eBPF RSS (can function with also with vhost=on) > + > +If steering BPF is not set for kernel's TUN module, the TUN uses automatic selection > +of rx virtqueue based on lookup table built according to calculated symmetric hash > +of transmitted packets. > +If steering BPF is set for TUN the BPF code calculates the hash of packet header and > +returns the virtqueue number to place the packet to. > + > +Simplified decision formula: > + > +.. code:: C > + > + queue_index = indirection_table[hash(<packet data>)%<indirection_table size>] > + > + > +Not for all packets, the hash can/should be calculated. > + > +Note: currently, eBPF RSS does not support hash reporting. > + > +eBPF RSS turned on by different combinations of vhost-net, vitrio-net and tap configurations: > + > +- eBPF is used: > + > + tap,vhost=off & virtio-net-pci,rss=on,hash=off > + > +- eBPF is used: > + > + tap,vhost=on & virtio-net-pci,rss=on,hash=off > + > +- 'software' RSS is used: > + > + tap,vhost=off & virtio-net-pci,rss=on,hash=on > + > +- eBPF is used, hash population feature is not reported to the guest: > + > + tap,vhost=on & virtio-net-pci,rss=on,hash=on > + > +If CONFIG_EBPF is not set then only 'software' RSS is supported. > +Also 'software' RSS, as a fallback, is used if the eBPF program failed to load or set to TUN. > + > +RSS eBPF program > +---------------- > + > +RSS program located in ebpf/tun_rss_steering.h as an array of 'struct bpf_insn'. > +So the program is part of the qemu binary. > +Initially, the eBPF program was compiled by clang and source code located at ebpf/rss.bpf.c. > +Prerequisites to recompile the eBPF program (regenerate ebpf/tun_rss_steering.h): > + > + llvm, clang, kernel source tree, python3 + (pip3 pyelftools) > + Adjust 'linuxhdrs' in Makefile.ebpf to reflect the location of the kernel source tree > + > + $ cd ebpf > + $ make -f Makefile.ebpf > + > +Note the python script for convertation from eBPF ELF object to '.h' file - Ebpf_to_C.py: > + > + $ python EbpfElf_to_C.py rss.bpf.o tun_rss_steering > + > +The first argument of the script is ELF object, second - section name where the eBPF program located. > +The script would generate <section name>.h file with eBPF instructions and 'relocate array'. > +'relocate array' is an array of 'struct fixup_mapfd_t' with the name of the eBPF map and instruction offset where the file descriptor of the map should be placed. > + Do we still need this if we decide to use llvm/clang toolchain? (I guess not) Thanks > +Current eBPF RSS implementation uses 'bounded loops' with 'backward jump instructions' which present in the last kernels. > +Overall eBPF RSS works on kernels 5.8+. > + > +eBPF RSS implementation > +----------------------- > + > +eBPF RSS loading functionality located in ebpf/ebpf_rss.c and ebpf/ebpf_rss.h. > + > +The `struct EBPFRSSContext` structure that holds 4 file descriptors: > + > +- program_fd - file descriptor of the eBPF RSS program. > +- map_configuration - file descriptor of the 'configuration' map. This map contains one element of 'struct EBPFRSSConfig'. This configuration determines eBPF program behavior. > +- map_toeplitz_key - file descriptor of the 'Toeplitz key' map. One element of the 40byte key prepared for the hashing algorithm. > +- map_indirections_table - 128 elements of queue indexes. > + > +`struct EBPFRSSConfig` fields: > + > +- redirect - "boolean" value, should the hash be calculated, on false - `default_queue` would be used as the final decision. > +- populate_hash - for now, not used. eBPF RSS doesn't support hash reporting. > +- hash_types - binary mask of different hash types. See `VIRTIO_NET_RSS_HASH_TYPE_*` defines. If for packet hash should not be calculated - `default_queue` would be used. > +- indirections_len - length of the indirections table, maximum 128. > +- default_queue - the queue index that used for packet that shouldn't be hashed. For some packets, the hash can't be calculated(g.e ARP). > + > +Functions: > + > +- `ebpf_rss_init()` - sets program_fd to -1, which indicates that EBPFRSSContext is not loaded. > +- `ebpf_rss_load()` - creates 3 maps and loads eBPF program from tun_rss_steering.h. Returns 'true' on success. After that, program_fd can be used to set steering for TAP. > +- `ebpf_rss_set_all()` - sets values for eBPF maps. `indirections_table` length is in EBPFRSSConfig. `toeplitz_key` is VIRTIO_NET_RSS_MAX_KEY_SIZE aka 40 bytes array. > +- `ebpf_rss_unload()` - close all file descriptors and set program_fd to -1. > + > +Simplified eBPF RSS workflow: > + > +.. code:: C > + > + struct EBPFRSSConfig config; > + config.redirect = 1; > + config.hash_types = VIRTIO_NET_RSS_HASH_TYPE_UDPv4 | VIRTIO_NET_RSS_HASH_TYPE_TCPv4; > + config.indirections_len = VIRTIO_NET_RSS_MAX_TABLE_LEN; > + config.default_queue = 0; > + > + uint16_t table[VIRTIO_NET_RSS_MAX_TABLE_LEN] = {...}; > + uint8_t key[VIRTIO_NET_RSS_MAX_KEY_SIZE] = {...}; > + > + struct EBPFRSSContext ctx; > + ebpf_rss_init(&ctx); > + ebpf_rss_load(&ctx); > + ebpf_rss_set_all(&ctx, &config, table, key); > + if (net_client->info->set_steering_ebpf != NULL) { > + net_client->info->set_steering_ebpf(net_client, ctx->program_fd); > + } > + ... > + ebpf_unload(&ctx); > + > + > +NetClientState SetSteeringEBPF() > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > + > +For now, `set_steering_ebpf()` method supported by Linux TAP NetClientState. The method requires an eBPF program file descriptor as an argument.
On 2020/11/3 上午2:51, Andrew Melnychenko wrote: > From: Andrew<andrew@daynix.com> > > Also, added maintainers information. > > Signed-off-by: Yuri Benditovich<yuri.benditovich@daynix.com> > Signed-off-by: Andrew Melnychenko<andrew@daynix.com> > --- > MAINTAINERS | 6 +++ > docs/ebpf.rst | 29 +++++++++++ > docs/ebpf_rss.rst | 129 ++++++++++++++++++++++++++++++++++++++++++++++ > 3 files changed, 164 insertions(+) > create mode 100644 docs/ebpf.rst > create mode 100644 docs/ebpf_rss.rst > > diff --git a/MAINTAINERS b/MAINTAINERS > index 2c22bbca5a..464b3f3c95 100644 > --- a/MAINTAINERS > +++ b/MAINTAINERS > @@ -3111,6 +3111,12 @@ S: Maintained > F: hw/semihosting/ > F: include/hw/semihosting/ > > +EBPF: > +M: Andrew Melnychenko<andrew@daynix.com> > +M: Yuri Benditovich<yuri.benditovich@daynix.com> > +S: Maintained > +F: ebpf/* > + If it's possible, I would like to be one of the maintainer or at least reviewer :) Thanks
On Thu, Nov 5, 2020 at 5:56 AM Jason Wang <jasowang@redhat.com> wrote: > > On 2020/11/3 上午2:51, Andrew Melnychenko wrote: > > From: Andrew<andrew@daynix.com> > > > > Also, added maintainers information. > > > > Signed-off-by: Yuri Benditovich<yuri.benditovich@daynix.com> > > Signed-off-by: Andrew Melnychenko<andrew@daynix.com> > > --- > > MAINTAINERS | 6 +++ > > docs/ebpf.rst | 29 +++++++++++ > > docs/ebpf_rss.rst | 129 ++++++++++++++++++++++++++++++++++++++++++++++ > > 3 files changed, 164 insertions(+) > > create mode 100644 docs/ebpf.rst > > create mode 100644 docs/ebpf_rss.rst > > > > diff --git a/MAINTAINERS b/MAINTAINERS > > index 2c22bbca5a..464b3f3c95 100644 > > --- a/MAINTAINERS > > +++ b/MAINTAINERS > > @@ -3111,6 +3111,12 @@ S: Maintained > > F: hw/semihosting/ > > F: include/hw/semihosting/ > > > > +EBPF: > > +M: Andrew Melnychenko<andrew@daynix.com> > > +M: Yuri Benditovich<yuri.benditovich@daynix.com> > > +S: Maintained > > +F: ebpf/* > > + > > > If it's possible, I would like to be one of the maintainer or at least > reviewer :) > > With pleasure. We did not know who would want to maintain eBPF related things, so we added ourselves as maintainers. If you agree, we'll place you as a maintainer and ourselves as reviewers to be informed about changes before they happen. Thanks > Thanks > >
diff --git a/MAINTAINERS b/MAINTAINERS index 2c22bbca5a..464b3f3c95 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -3111,6 +3111,12 @@ S: Maintained F: hw/semihosting/ F: include/hw/semihosting/ +EBPF: +M: Andrew Melnychenko <andrew@daynix.com> +M: Yuri Benditovich <yuri.benditovich@daynix.com> +S: Maintained +F: ebpf/* + Build and test automation ------------------------- Build and test automation diff --git a/docs/ebpf.rst b/docs/ebpf.rst new file mode 100644 index 0000000000..e45d085432 --- /dev/null +++ b/docs/ebpf.rst @@ -0,0 +1,29 @@ +=========================== +eBPF qemu support +=========================== + +eBPF support (CONFIG_EBPF) is enabled automatically by 'configure' script +if 'bpf' system call is available. +To disable eBPF support use './configure --disable-bpf' + +Basic eBPF functionality is located in ebpf/ebpf.c and ebpf/ebpf.h. +There are basic functions to load the eBPF program into the kernel. +Mostly, functions name are self-explanatory: + +- `bpf_create_map()`, `bpf_lookup_element()`, `bpf_update_element()`, `bpf_delete_element()` - manages eBPF maps. On error, a basic error message would be reported and returned -1. On success, 0 would be returned(`bpf_create_map()` returns map's file descriptor). +- `bpf_prog_load()` - load the program. The program has to have proper map file descriptors if there are used. On error - the log eBPF would be reported. On success, the program file descriptor returned. +- `bpf_fixup_mapfd()` - would place map file descriptor into the program according to 'relocate array' of 'struct fixup_mapfd_t'. The function would return how many instructions were 'fixed' aka how many relocations was occurred. + +Simplified workflow would look like this: + +.. code:: C + + int map1 = bpf_create_map(...); + int map2 = bpf_create_map(...); + + bpf_fixup_mapfd(<fixup table>, ARRAY_SIZE(<fixup table>), <instructions pointer>, ARRAY_SIZE(<instructions pointer>), <map1 name>, map1); + bpf_fixup_mapfd(<fixup table>, ARRAY_SIZE(<fixup table>), <instructions pointer>, ARRAY_SIZE(<instructions pointer>), <map2 name>, map2); + + int prog = bpf_prog_load(<program type>, <instructions pointer>, ARRAY_SIZE(<instructions pointer>), "GPL"); + +See the bpf(2) for details. diff --git a/docs/ebpf_rss.rst b/docs/ebpf_rss.rst new file mode 100644 index 0000000000..96fee391b8 --- /dev/null +++ b/docs/ebpf_rss.rst @@ -0,0 +1,129 @@ +=========================== +eBPF RSS virtio-net support +=========================== + +RSS(Receive Side Scaling) is used to distribute network packets to guest virtqueues +by calculating packet hash. Usually every queue is processed then by a specific guest CPU core. + +For now there are 2 RSS implementations in qemu: +- 'software' RSS (functions if qemu receives network packets, i.e. vhost=off) +- eBPF RSS (can function with also with vhost=on) + +If steering BPF is not set for kernel's TUN module, the TUN uses automatic selection +of rx virtqueue based on lookup table built according to calculated symmetric hash +of transmitted packets. +If steering BPF is set for TUN the BPF code calculates the hash of packet header and +returns the virtqueue number to place the packet to. + +Simplified decision formula: + +.. code:: C + + queue_index = indirection_table[hash(<packet data>)%<indirection_table size>] + + +Not for all packets, the hash can/should be calculated. + +Note: currently, eBPF RSS does not support hash reporting. + +eBPF RSS turned on by different combinations of vhost-net, vitrio-net and tap configurations: + +- eBPF is used: + + tap,vhost=off & virtio-net-pci,rss=on,hash=off + +- eBPF is used: + + tap,vhost=on & virtio-net-pci,rss=on,hash=off + +- 'software' RSS is used: + + tap,vhost=off & virtio-net-pci,rss=on,hash=on + +- eBPF is used, hash population feature is not reported to the guest: + + tap,vhost=on & virtio-net-pci,rss=on,hash=on + +If CONFIG_EBPF is not set then only 'software' RSS is supported. +Also 'software' RSS, as a fallback, is used if the eBPF program failed to load or set to TUN. + +RSS eBPF program +---------------- + +RSS program located in ebpf/tun_rss_steering.h as an array of 'struct bpf_insn'. +So the program is part of the qemu binary. +Initially, the eBPF program was compiled by clang and source code located at ebpf/rss.bpf.c. +Prerequisites to recompile the eBPF program (regenerate ebpf/tun_rss_steering.h): + + llvm, clang, kernel source tree, python3 + (pip3 pyelftools) + Adjust 'linuxhdrs' in Makefile.ebpf to reflect the location of the kernel source tree + + $ cd ebpf + $ make -f Makefile.ebpf + +Note the python script for convertation from eBPF ELF object to '.h' file - Ebpf_to_C.py: + + $ python EbpfElf_to_C.py rss.bpf.o tun_rss_steering + +The first argument of the script is ELF object, second - section name where the eBPF program located. +The script would generate <section name>.h file with eBPF instructions and 'relocate array'. +'relocate array' is an array of 'struct fixup_mapfd_t' with the name of the eBPF map and instruction offset where the file descriptor of the map should be placed. + +Current eBPF RSS implementation uses 'bounded loops' with 'backward jump instructions' which present in the last kernels. +Overall eBPF RSS works on kernels 5.8+. + +eBPF RSS implementation +----------------------- + +eBPF RSS loading functionality located in ebpf/ebpf_rss.c and ebpf/ebpf_rss.h. + +The `struct EBPFRSSContext` structure that holds 4 file descriptors: + +- program_fd - file descriptor of the eBPF RSS program. +- map_configuration - file descriptor of the 'configuration' map. This map contains one element of 'struct EBPFRSSConfig'. This configuration determines eBPF program behavior. +- map_toeplitz_key - file descriptor of the 'Toeplitz key' map. One element of the 40byte key prepared for the hashing algorithm. +- map_indirections_table - 128 elements of queue indexes. + +`struct EBPFRSSConfig` fields: + +- redirect - "boolean" value, should the hash be calculated, on false - `default_queue` would be used as the final decision. +- populate_hash - for now, not used. eBPF RSS doesn't support hash reporting. +- hash_types - binary mask of different hash types. See `VIRTIO_NET_RSS_HASH_TYPE_*` defines. If for packet hash should not be calculated - `default_queue` would be used. +- indirections_len - length of the indirections table, maximum 128. +- default_queue - the queue index that used for packet that shouldn't be hashed. For some packets, the hash can't be calculated(g.e ARP). + +Functions: + +- `ebpf_rss_init()` - sets program_fd to -1, which indicates that EBPFRSSContext is not loaded. +- `ebpf_rss_load()` - creates 3 maps and loads eBPF program from tun_rss_steering.h. Returns 'true' on success. After that, program_fd can be used to set steering for TAP. +- `ebpf_rss_set_all()` - sets values for eBPF maps. `indirections_table` length is in EBPFRSSConfig. `toeplitz_key` is VIRTIO_NET_RSS_MAX_KEY_SIZE aka 40 bytes array. +- `ebpf_rss_unload()` - close all file descriptors and set program_fd to -1. + +Simplified eBPF RSS workflow: + +.. code:: C + + struct EBPFRSSConfig config; + config.redirect = 1; + config.hash_types = VIRTIO_NET_RSS_HASH_TYPE_UDPv4 | VIRTIO_NET_RSS_HASH_TYPE_TCPv4; + config.indirections_len = VIRTIO_NET_RSS_MAX_TABLE_LEN; + config.default_queue = 0; + + uint16_t table[VIRTIO_NET_RSS_MAX_TABLE_LEN] = {...}; + uint8_t key[VIRTIO_NET_RSS_MAX_KEY_SIZE] = {...}; + + struct EBPFRSSContext ctx; + ebpf_rss_init(&ctx); + ebpf_rss_load(&ctx); + ebpf_rss_set_all(&ctx, &config, table, key); + if (net_client->info->set_steering_ebpf != NULL) { + net_client->info->set_steering_ebpf(net_client, ctx->program_fd); + } + ... + ebpf_unload(&ctx); + + +NetClientState SetSteeringEBPF() +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +For now, `set_steering_ebpf()` method supported by Linux TAP NetClientState. The method requires an eBPF program file descriptor as an argument.