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Mon, 08 Jul 2019 09:13:39 -0700 (PDT) Date: Mon, 8 Jul 2019 09:13:38 -0700 From: Stanislav Fomichev To: Y Song Cc: Stanislav Fomichev , netdev , bpf , David Miller , Alexei Starovoitov , Daniel Borkmann , Ilya Leoshkevich Subject: Re: [PATCH bpf-next] selftests/bpf: make verifier loop tests arch independent Message-ID: <20190708161338.GC29524@mini-arch> References: <20190703205100.142904-1-sdf@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.12.1 (2019-06-15) Sender: bpf-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On 07/03, Y Song wrote: > On Wed, Jul 3, 2019 at 1:51 PM Stanislav Fomichev wrote: > > > > Take the first x bytes of pt_regs for scalability tests, there is > > no real reason we need x86 specific rax. > > > > Signed-off-by: Stanislav Fomichev > > --- > > tools/testing/selftests/bpf/progs/loop1.c | 3 ++- > > tools/testing/selftests/bpf/progs/loop2.c | 3 ++- > > tools/testing/selftests/bpf/progs/loop3.c | 3 ++- > > 3 files changed, 6 insertions(+), 3 deletions(-) > > > > diff --git a/tools/testing/selftests/bpf/progs/loop1.c b/tools/testing/selftests/bpf/progs/loop1.c > > index dea395af9ea9..d530c61d2517 100644 > > --- a/tools/testing/selftests/bpf/progs/loop1.c > > +++ b/tools/testing/selftests/bpf/progs/loop1.c > > @@ -14,11 +14,12 @@ SEC("raw_tracepoint/kfree_skb") > > int nested_loops(volatile struct pt_regs* ctx) > > { > > int i, j, sum = 0, m; > > + volatile int *any_reg = (volatile int *)ctx; > > > > for (j = 0; j < 300; j++) > > for (i = 0; i < j; i++) { > > if (j & 1) > > - m = ctx->rax; > > + m = *any_reg; > > I agree. ctx->rax here is only to generate some operations, which > cannot be optimized away by the compiler. dereferencing a volatile > pointee may just serve that purpose. > > Comparing the byte code generated with ctx->rax and *any_reg, they are > slightly different. Using *any_reg is slighly worse, but this should > be still okay for the test. > > > else > > m = j; > > sum += i * m; > > diff --git a/tools/testing/selftests/bpf/progs/loop2.c b/tools/testing/selftests/bpf/progs/loop2.c > > index 0637bd8e8bcf..91bb89d901e3 100644 > > --- a/tools/testing/selftests/bpf/progs/loop2.c > > +++ b/tools/testing/selftests/bpf/progs/loop2.c > > @@ -14,9 +14,10 @@ SEC("raw_tracepoint/consume_skb") > > int while_true(volatile struct pt_regs* ctx) > > { > > int i = 0; > > + volatile int *any_reg = (volatile int *)ctx; > > > > while (true) { > > - if (ctx->rax & 1) > > + if (*any_reg & 1) > > i += 3; > > else > > i += 7; > > diff --git a/tools/testing/selftests/bpf/progs/loop3.c b/tools/testing/selftests/bpf/progs/loop3.c > > index 30a0f6cba080..3a7f12d7186c 100644 > > --- a/tools/testing/selftests/bpf/progs/loop3.c > > +++ b/tools/testing/selftests/bpf/progs/loop3.c > > @@ -14,9 +14,10 @@ SEC("raw_tracepoint/consume_skb") > > int while_true(volatile struct pt_regs* ctx) > > { > > __u64 i = 0, sum = 0; > > + volatile __u64 *any_reg = (volatile __u64 *)ctx; > > do { > > i++; > > - sum += ctx->rax; > > + sum += *any_reg; > > } while (i < 0x100000000ULL); > > return sum; > > } > > -- > > 2.22.0.410.gd8fdbe21b5-goog > > Ilya Leoshkevich (iii@linux.ibm.com, cc'ed) has another patch set > trying to solve this problem by introducing s360 arch register access > macros. I guess for now that patch set is not needed any more? Oh, I missed them. Do they fix the tests for other (non-s360) arches as well? I was trying to fix the issue by not depending on any arch specific stuff because the test really doesn't care :-)