netdev - Re: [RFC PATCH v2 08/10] selftests: conditionally enable XDP support in udpgso_bench

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Date:   Sun, 21 Oct 2018 16:09:16 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Paolo Abeni <pabeni@...hat.com>
Cc:     Network Development <netdev@...r.kernel.org>,
        Willem de Bruijn <willemb@...gle.com>,
        steffen.klassert@...unet.com
Subject: Re: [RFC PATCH v2 08/10] selftests: conditionally enable XDP support
 in udpgso_bench_rx

On Fri, Oct 19, 2018 at 10:31 AM Paolo Abeni <pabeni@...hat.com> wrote:
>
> XDP support will be used by a later patch to test the GRO path
> in a net namespace, leveraging the veth XDP implementation.
> To avoid breaking existing setup, XDP support is conditionally
> enabled and build only if llc is locally available.
>
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>
> ---
> diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
> index 256d82d5fa87..176459b7c4d6 100644
> --- a/tools/testing/selftests/net/Makefile
> +++ b/tools/testing/selftests/net/Makefile
> @@ -16,8 +16,77 @@ TEST_GEN_PROGS = reuseport_bpf reuseport_bpf_cpu reuseport_bpf_numa
>  TEST_GEN_PROGS += reuseport_dualstack reuseaddr_conflict tls
>
>  KSFT_KHDR_INSTALL := 1
> +
> +# Allows pointing LLC/CLANG to a LLVM backend with bpf support, redefine on cmdline:
> +#  make samples/bpf/ LLC=~/git/llvm/build/bin/llc CLANG=~/git/llvm/build/bin/clang
> +LLC ?= llc
> +CLANG ?= clang
> +LLVM_OBJCOPY ?= llvm-objcopy
> +BTF_PAHOLE ?= pahole
> +HAS_LLC := $(shell which $(LLC) 2>/dev/null)
> +
> +# conditional enable testes requiring llc
> +ifneq (, $(HAS_LLC))
> +TEST_GEN_FILES += xdp_dummy.o
> +endif
> +
>  include ../lib.mk
>
> +ifneq (, $(HAS_LLC))
> +
> +# Detect that we're cross compiling and use the cross compiler
> +ifdef CROSS_COMPILE
> +CLANG_ARCH_ARGS = -target $(ARCH)
> +endif
> +
> +PROBE := $(shell $(LLC) -march=bpf -mcpu=probe -filetype=null /dev/null 2>&1)
> +
> +# Let newer LLVM versions transparently probe the kernel for availability
> +# of full BPF instruction set.
> +ifeq ($(PROBE),)
> +  CPU ?= probe
> +else
> +  CPU ?= generic
> +endif
> +
> +SRC_PATH := $(abspath ../../../..)
> +LIB_PATH := $(SRC_PATH)/tools/lib
> +XDP_CFLAGS := -D SUPPORT_XDP=1 -I$(LIB_PATH)
> +LIBBPF = $(LIB_PATH)/bpf/libbpf.a
> +BTF_LLC_PROBE := $(shell $(LLC) -march=bpf -mattr=help 2>&1 | grep dwarfris)
> +BTF_PAHOLE_PROBE := $(shell $(BTF_PAHOLE) --help 2>&1 | grep BTF)
> +BTF_OBJCOPY_PROBE := $(shell $(LLVM_OBJCOPY) --help 2>&1 | grep -i 'usage.*llvm')
> +CLANG_SYS_INCLUDES := $(shell $(CLANG) -v -E - </dev/null 2>&1 \
> +        | sed -n '/<...> search starts here:/,/End of search list./{ s| \(/.*\)|-idirafter \1|p }')
> +CLANG_FLAGS = -I. -I$(SRC_PATH)/include -I../bpf/ \
> +             $(CLANG_SYS_INCLUDES) -Wno-compare-distinct-pointer-types
> +
> +ifneq ($(and $(BTF_LLC_PROBE),$(BTF_PAHOLE_PROBE),$(BTF_OBJCOPY_PROBE)),)
> +       CLANG_CFLAGS += -g
> +       LLC_FLAGS += -mattr=dwarfris
> +       DWARF2BTF = y
> +endif
> +
> +$(LIBBPF): FORCE
> +# Fix up variables inherited from Kbuild that tools/ build system won't like
> +       $(MAKE) -C $(dir $@) RM='rm -rf' LDFLAGS= srctree=$(SRC_PATH) O= $(nodir $@)
> +

This is a lot of XDP specific code. Not for this patchset, per se, but
would be nice if we can reuse the logic in selftests/bpf for all this.

> --- a/tools/testing/selftests/net/udpgso_bench_rx.c
> @@ -227,6 +234,13 @@ static void parse_opts(int argc, char **argv)
>                         cfg_verify = true;
>                         cfg_read_all = true;
>                         break;
> +#ifdef SUPPORT_XDP
> +               case 'x':
> +                       cfg_xdp_iface = if_nametoindex(optarg);
> +                       if (!cfg_xdp_iface)
> +                               error(1, errno, "unknown interface %s", optarg);
> +                       break;
> +#endif

nit: needs to be added to getopt string in this patch.