On 10/29/2018 11:11 PM, John Fastabend wrote:
> On 10/29/2018 02:19 PM, Shannon Nelson wrote:
>> This is an example of using XDP to redirect the processing of
>> particular vlan packets to specific CPUs. This is in response
>> to comments received on a kernel patch put forth previously
>> to do something similar using RPS.
>> https://www.spinics.net/lists/netdev/msg528210.html
>> [PATCH net-next] net: enable RPS on vlan devices
>>
>> This XDP application watches for inbound vlan-tagged packets
>> and redirects those packets to be processed on a specific CPU
>> as configured in a BPF map. The BPF map can be modified by
>> this user program, which can also load and unload the kernel
>> XDP code.
>>
>> One example use is for supporting VMs where we can't control the
>> OS being used: we'd like to separate the VM CPU processing from
>> the host's CPUs as a way to help mitigate L1TF related issues.
>> When running the VM's traffic on a vlan we can stick the host's
>> Rx processing on one set of CPUs separate from the VM's CPUs.
>>
>> This example currently uses a vlan key and cpu value in the
>> BPF map, so only can do one CPU per vlan. This could easily
>> be modified to use a bitpattern of CPUs rather than a CPU id
>> to allow multiple CPUs per vlan.
>
> Great, so does this solve your use case then? At least on drivers
> with XDP support?
>
>>
>> Signed-off-by: Shannon Nelson <shannon.nel...@oracle.com>
>> ---
>
> Some really small and trivial nits below.
>
> Acked-by: John Fastabend <john.fastab...@gmail.com>
>
> [...]
>
>> + if (install) {
>> +
>
> new line probably not needed.
>
>> + /* check to see if already installed */
>> + errno = 0;
>> + access(pin_prog_name, R_OK);
>> + if (errno != ENOENT) {
>> + fprintf(stderr, "ERR: %s is already installed\n",
>> argv[0]);
>> + return -1;
>> + }
>> +
>> + /* load the XDP program and maps with the convenient library */
>> + if (load_bpf_file(filename)) {
>> + fprintf(stderr, "ERR: load_bpf_file(%s): \n%s",
>> + filename, bpf_log_buf);
>> + return -1;
>> + }
>> + if (!prog_fd[0]) {
>> + fprintf(stderr, "ERR: load_bpf_file(%s): %d %s\n",
>> + filename, errno, strerror(errno));
>> + return -1;
>> + }
>> +
>> + /* pin the XDP program and maps */
>> + if (bpf_obj_pin(prog_fd[0], pin_prog_name) < 0) {
>> + fprintf(stderr, "ERR: bpf_obj_pin(%s): %d %s\n",
>> + pin_prog_name, errno, strerror(errno));
>> + if (errno == 2)
>> + fprintf(stderr, " (is the BPF fs mounted on
>> /sys/fs/bpf?)\n");
>> + return -1;
>> + }
>> + if (bpf_obj_pin(map_fd[0], pin_vlanmap_name) < 0) {
>> + fprintf(stderr, "ERR: bpf_obj_pin(%s): %d %s\n",
>> + pin_vlanmap_name, errno, strerror(errno));
>> + return -1;
>> + }
>> + if (bpf_obj_pin(map_fd[2], pin_countermap_name) < 0) {
>> + fprintf(stderr, "ERR: bpf_obj_pin(%s): %d %s\n",
>> + pin_countermap_name, errno, strerror(errno));
>> + return -1;
>> + }
>> +
>> + /* prep the vlan map with "not used" values */
>> + c64 = UNDEF_CPU;
>> + for (v64 = 0; v64 < 4096; v64++) {
>
> maybe #define MAX_VLANS 4096 just to avoid constants.
>
>> + if (bpf_map_update_elem(map_fd[0], &v64, &c64, 0)) {
>> + fprintf(stderr, "ERR: preping vlan map failed
>> on v=%llu: %d %s\n",
>> + v64, errno, strerror(errno));
>> + return -1;
>> + }
>> + }
>> +
>> + /* prep the cpumap with queue sizes */
>> + c64 = 128+64; /* see note in xdp_redirect_cpu_user.c */
>> + for (v64 = 0; v64 < MAX_CPUS; v64++) {
>> + if (bpf_map_update_elem(map_fd[1], &v64, &c64, 0)) {
>> + if (errno == ENODEV) {
>> + /* Save the last CPU number attempted
>> + * into the counters map
>> + */
>> + c64 = CPU_COUNT;
>> + ret = bpf_map_update_elem(map_fd[2],
>> &c64, &v64, 0);
>> + break;
>> + }
>> +
>> + fprintf(stderr, "ERR: preping cpu map failed on
>> v=%llu: %d %s\n",
>> + v64, errno, strerror(errno));
>> + return -1;
>> + }
>> + }
>> +
>> + /* wire the XDP program to the device */
>> + if (bpf_set_link_xdp_fd(ifindex, prog_fd[0], 0) < 0) {
>> + fprintf(stderr, "ERR: bpf_set_link_xdp_fd(): %d %s\n",
>> + errno, strerror(errno));
>> + return -1;
>> + }
>> +
>> + return 0;
>> + }
>> +
>> + if (remove) {
>> +
Ditto
>> + /* unlink the program from the device */
>> + if (bpf_set_link_xdp_fd(ifindex, -1, 0) < 0)
>> + fprintf(stderr, "ERR: bpf_set_link_xdp_fd(): %d %s\n",
>> + errno, strerror(errno));
>> +
>> + /* unlink pinned files */
>> + if (unlink(pin_prog_name))
>> + fprintf(stderr, "ERR: unlink(%s): %d %s\n",
>> + pin_prog_name, errno, strerror(errno));
>> + if (unlink(pin_vlanmap_name))
>> + fprintf(stderr, "ERR: unlink(%s): %d %s\n",
>> + pin_vlanmap_name, errno, strerror(errno));
>> + if (unlink(pin_countermap_name))
>> + fprintf(stderr, "ERR: unlink(%s): %d %s\n",
>> + pin_countermap_name, errno, strerror(errno));
>> +
>> + return 0;
>> + }
>> +
>> + if (vlan == 0) {
>> + fprintf(stderr, "ERR: required option --vlan missing\n");
>> + goto error;
>> + }
>> +
>> + if (cpu == MAX_CPUS && vlan > 0) {
>> + fprintf(stderr, "ERR: required option --cpu missing\n");
>> + goto error;
>> + }
>> +
>> + vfd = bpf_obj_get(pin_vlanmap_name);
>> + if (vfd < 0) {
>> + fprintf(stderr, "ERR: can't find pinned map %s: %d %s\n",
>> + pin_vlanmap_name, errno, strerror(errno));
>> + if (errno == ENOENT)
>> + fprintf(stderr, " (has %s been installed yet?)\n",
>> argv[0]);
>> + return -1;
>> + }
>> +
>> + /* decode the requested action */
>> + if (vlan > 0) {
>> + /* check cpu against the max value found */
>> + cfd = bpf_obj_get(pin_countermap_name);
>> + if (cfd < 0) {
>> + fprintf(stderr, "ERR: can't find pinned map %s: %d
>> %s\n",
>> + pin_countermap_name, errno, strerror(errno));
>> + return -1;
>> + }
>> + c64 = CPU_COUNT;
>> + ret = bpf_map_lookup_elem(cfd, &c64, &v64);
>> + if (cpu >= v64) {
>
> Need to check ret code?
Yeah, I expect this would have another respin, thanks!
>> + fprintf(stderr, "ERR: cpu %d greater than max %llu\n",
>> cpu, v64);
>> + return -1;
>> + }
>> +
>> + /* Note that the value and key pointers really do need to be
>> + * pointers to 64-bit values, else things get a bit muddled.
>> + */
>> + v64 = vlan;
>> + c64 = cpu;
>> + ret = bpf_map_update_elem(vfd, &v64, &c64, 0);
>> + if (ret) {
>> + fprintf(stderr, "Adding vlan %d CPU %d failed: %d %s\n",
>> + vlan, cpu, errno, strerror(errno));
>> + return -1;
>> + }
>> +
>> + } else {
>> + v64 = -vlan;
>> + c64 = UNDEF_CPU;
>> +
>> + /* We can't actually delete from a TYPE_ARRAY map, so we
>> + * simply set it to an undefined value.
>> + */
>> + ret = bpf_map_update_elem(vfd, &v64, &c64, 0);
>> + if (ret) {
>> + fprintf(stderr, "Delete of vlan %llu failed: %d %s\n",
>> + v64, errno, strerror(errno));
>> + return -1;
>> + }
>> + }
>> +
>> + return 0;
>> +
>> +error:
>> + usage(argv);
>> + return -1;
>> +}
>>
>
