Le 18/11/2022 à 09:39, Hari Bathini a écrit : > > > On 17/11/22 12:29 pm, Christophe Leroy wrote: >> >> >> Le 16/11/2022 à 18:01, Hari Bathini a écrit : >>> >>> >>> On 16/11/22 12:14 am, Christophe Leroy wrote: >>>> >>>> >>>> Le 14/11/2022 à 18:27, Christophe Leroy a écrit : >>>>> >>>>> >>>>> Le 14/11/2022 à 15:47, Hari Bathini a écrit : >>>>>> Hi Christophe, >>>>>> >>>>>> On 11/11/22 4:55 pm, Christophe Leroy wrote: >>>>>>> Le 10/11/2022 à 19:43, Hari Bathini a écrit : >>>>>>>> Most BPF programs are small, but they consume a page each. For >>>>>>>> systems >>>>>>>> with busy traffic and many BPF programs, this may also add >>>>>>>> significant >>>>>>>> pressure on instruction TLB. High iTLB pressure usually slows down >>>>>>>> the >>>>>>>> whole system causing visible performance degradation for production >>>>>>>> workloads. >>>>>>>> >>>>>>>> bpf_prog_pack, a customized allocator that packs multiple bpf >>>>>>>> programs >>>>>>>> into preallocated memory chunks, was proposed [1] to address it. >>>>>>>> This >>>>>>>> series extends this support on powerpc. >>>>>>>> >>>>>>>> Patches 1 & 2 add the arch specific functions needed to support >>>>>>>> this >>>>>>>> feature. Patch 3 enables the support for powerpc. The last patch >>>>>>>> ensures cleanup is handled racefully. >>>>>>>> >>>>>> >>>>>>>> Tested the changes successfully on a PowerVM. patch_instruction(), >>>>>>>> needed for bpf_arch_text_copy(), is failing for ppc32. Debugging >>>>>>>> it. >>>>>>>> Posting the patches in the meanwhile for feedback on these changes. >>>>>>> >>>>>>> I did a quick test on ppc32, I don't get such a problem, only >>>>>>> something >>>>>>> wrong in the dump print as traps intructions only are dumped, but >>>>>>> tcpdump works as expected: >>>>>> >>>>>> Thanks for the quick test. Could you please share the config you >>>>>> used. >>>>>> I am probably missing a few knobs in my conifg... >>>>>> >>>>> >>>> >>>> I also managed to test it on QEMU. The config is based on >>>> pmac32_defconfig. >>> >>> I had the same config but hit this problem: >>> >>> # echo 1 > /proc/sys/net/core/bpf_jit_enable; modprobe test_bpf >>> test_bpf: #0 TAX >>> ------------[ cut here ]------------ >>> WARNING: CPU: 0 PID: 96 at arch/powerpc/net/bpf_jit_comp.c:367 >>> bpf_int_jit_compile+0x8a0/0x9f8 >> >> I get no such problem, on QEMU, and I checked the .config has: > >> CONFIG_STRICT_KERNEL_RWX=y >> CONFIG_STRICT_MODULE_RWX=y > > Yeah. That did the trick. Interesting. I guess we have to find out why it fails when those config are missing. Maybe module code plays with RO and NX flags even if CONFIG_STRICT_MODULE_RWX is not selected ? Christophe
