From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S944704AbdEZTXM (ORCPT ); Fri, 26 May 2017 15:23:12 -0400 Received: from www62.your-server.de ([213.133.104.62]:59991 "EHLO www62.your-server.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753318AbdEZTXG (ORCPT ); Fri, 26 May 2017 15:23:06 -0400 Message-ID: <59288093.8080108@iogearbox.net> Date: Fri, 26 May 2017 21:22:59 +0200 From: Daniel Borkmann User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.7.0 MIME-Version: 1.0 To: David Daney , David Daney , Alexei Starovoitov , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mips@linux-mips.org, ralf@linux-mips.org CC: Markos Chandras Subject: Re: [PATCH 5/5] MIPS: Add support for eBPF JIT. References: <20170526003826.10834-1-david.daney@cavium.com> <20170526003826.10834-6-david.daney@cavium.com> <5928463C.5000204@iogearbox.net> <59287D71.6000307@iogearbox.net> <9fcd54f8-ab2f-84aa-7db4-2165b746d7c3@caviumnetworks.com> In-Reply-To: <9fcd54f8-ab2f-84aa-7db4-2165b746d7c3@caviumnetworks.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-Authenticated-Sender: daniel@iogearbox.net Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/26/2017 09:20 PM, David Daney wrote: > On 05/26/2017 12:09 PM, Daniel Borkmann wrote: >> On 05/26/2017 05:39 PM, David Daney wrote: >>> On 05/26/2017 08:14 AM, Daniel Borkmann wrote: >>>> On 05/26/2017 02:38 AM, David Daney wrote: >>>>> Since the eBPF machine has 64-bit registers, we only support this in >>>>> 64-bit kernels. As of the writing of this commit log test-bpf is showing: >>>>> >>>>> test_bpf: Summary: 316 PASSED, 0 FAILED, [308/308 JIT'ed] >>>>> >>>>> All current test cases are successfully compiled. >>>>> >>>>> Signed-off-by: David Daney >>>> >>>> Awesome work! >>>> >>>> Did you also manage to run tools/testing/selftests/bpf/ fine with >>>> the JIT enabled? >>> >>> I haven't done that yet, I will before the next revision. >>> >>>> [...] >>>>> +struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) >>>>> +{ >>>>> + struct jit_ctx ctx; >>>>> + unsigned int alloc_size; >>>>> + >>>>> + /* Only 64-bit kernel supports eBPF */ >>>>> + if (!IS_ENABLED(CONFIG_64BIT) || !bpf_jit_enable) >>>> >>>> Isn't this already reflected by the following? >>>> >>>> select HAVE_EBPF_JIT if (64BIT && !CPU_MICROMIPS) >>> >>> Not exactly. The eBPF JIT is in the same file as the classic-BPF JIT, so when HAVE_EBPF_JIT is false this will indeed never be called. But the kernel would otherwise contain all the JIT code. >>> >>> By putting in !IS_ENABLED(CONFIG_64BIT) we allow gcc to eliminate all the dead code when compiling the JITs. >> >> Side-effect would still be that for cBPF you go through the cBPF >> JIT instead of letting the kernel convert all cBPF to eBPF and >> later on go through your eBPF JIT. If you still prefer to have >> everything in one single file and let gcc eliminate dead code >> then you can just do single line change ... >> >> void bpf_jit_compile(struct bpf_prog *fp) >> { >> struct jit_ctx ctx; >> unsigned int alloc_size, tmp_idx; >> >> if (IS_ENABLED(CONFIG_HAVE_EBPF_JIT) || !bpf_jit_enable) >> return; > > Yes. In fact I did that for testing. > > The cBPF JIT generates smaller code for: > > test_bpf: #274 BPF_MAXINSNS: ld_abs+get_processor_id jited:1 44128 PASS > > When we attempt to use the eBPF JIT for this, some of the MIPS branch instructions cannot reach their targets (+- 32K instructions). I didn't feel like fixing the code generation quite yet to handle branches that span more than 32K instructions, so I left the cBPF in place so I could claim that all of the test cases were JITed :-) > > For the next revision of the patch I will revisit this. Okay, sounds good!