| Message ID | 20210310080929.641212-3-bjorn.topel@gmail.com (mailing list archive) |
|---|---|
| State | Accepted |
| Delegated to: | BPF |
| Headers | show |
| Series | libbpf/xsk cleanups | expand |
On Wed, Mar 10, 2021 at 12:09 AM Björn Töpel <bjorn.topel@gmail.com> wrote: > > From: Björn Töpel <bjorn.topel@intel.com> > > The only user of libbpf_util.h is xsk.h. Move the barriers to xsk.h, > and remove libbpf_util.h. The barriers are used as an implementation > detail, and should not be considered part of the stable API. > > Signed-off-by: Björn Töpel <bjorn.topel@intel.com> > --- > tools/lib/bpf/Makefile | 1 - > tools/lib/bpf/libbpf_util.h | 82 ------------------------------------- > tools/lib/bpf/xsk.h | 68 +++++++++++++++++++++++++++++- > 3 files changed, 67 insertions(+), 84 deletions(-) > delete mode 100644 tools/lib/bpf/libbpf_util.h > [...] > diff --git a/tools/lib/bpf/xsk.h b/tools/lib/bpf/xsk.h > index a9fdea87b5cd..1d846a419d21 100644 > --- a/tools/lib/bpf/xsk.h > +++ b/tools/lib/bpf/xsk.h > @@ -4,6 +4,7 @@ > * AF_XDP user-space access library. > * > * Copyright(c) 2018 - 2019 Intel Corporation. Couldn't unsee ^this mismatch. Added space there. Also, removing libbpf_util.h caused incremental build failure for the kernel due to cached dependency files. make clean solved the issue. So just FYI for everyone. Applied to bpf-next, thanks. > + * Copyright (c) 2019 Facebook > * > * Author(s): Magnus Karlsson <magnus.karlsson@intel.com> > */ > @@ -13,15 +14,80 @@ > > #include <stdio.h> > #include <stdint.h> > +#include <stdbool.h> > #include <linux/if_xdp.h> > > #include "libbpf.h" > -#include "libbpf_util.h" > > #ifdef __cplusplus > extern "C" { > #endif > [...]
On Wed, Mar 10, 2021 at 09:09:29AM +0100, Björn Töpel wrote: > From: Björn Töpel <bjorn.topel@intel.com> > > The only user of libbpf_util.h is xsk.h. Move the barriers to xsk.h, > and remove libbpf_util.h. The barriers are used as an implementation > detail, and should not be considered part of the stable API. Does that mean that anything else which uses the same type of shared rings (bpf ringbuffer, io_uring, zctap) have to implement the same primitives that xsk.h has?
On 2021-03-11 01:06, Jonathan Lemon wrote: > On Wed, Mar 10, 2021 at 09:09:29AM +0100, Björn Töpel wrote: >> From: Björn Töpel <bjorn.topel@intel.com> >> >> The only user of libbpf_util.h is xsk.h. Move the barriers to xsk.h, >> and remove libbpf_util.h. The barriers are used as an implementation >> detail, and should not be considered part of the stable API. > > Does that mean that anything else which uses the same type of > shared rings (bpf ringbuffer, io_uring, zctap) have to implement > the same primitives that xsk.h has? > Jonathan, there's a longer explanation on back-/forward-compatibility in the commit message [1]. Again, this is for the XDP socket rings, so I wont comment on the other rings. I would not assume compatibility between different rings (e.g. the bpf ringbuffer and XDP sockets rings), not even prior the barrier change. Björn [1] https://lore.kernel.org/bpf/20210305094113.413544-2-bjorn.topel@gmail.com/
On Wed, Mar 10, 2021 at 10:59 PM Björn Töpel <bjorn.topel@intel.com> wrote: > > On 2021-03-11 01:06, Jonathan Lemon wrote: > > On Wed, Mar 10, 2021 at 09:09:29AM +0100, Björn Töpel wrote: > >> From: Björn Töpel <bjorn.topel@intel.com> > >> > >> The only user of libbpf_util.h is xsk.h. Move the barriers to xsk.h, > >> and remove libbpf_util.h. The barriers are used as an implementation > >> detail, and should not be considered part of the stable API. > > > > Does that mean that anything else which uses the same type of > > shared rings (bpf ringbuffer, io_uring, zctap) have to implement > > the same primitives that xsk.h has? > > > > Jonathan, there's a longer explanation on back-/forward-compatibility in > the commit message [1]. Again, this is for the XDP socket rings, so I > wont comment on the other rings. I would not assume compatibility > between different rings (e.g. the bpf ringbuffer and XDP sockets rings), > not even prior the barrier change. > > BPF ringbuf is using smp_store_release()/smp_load_acquire(), which are coming from asm/barrier.h. But libbpf abstracts all the low-level details, so users don't have to use such low-level primitives directly. > Björn > > [1] > https://lore.kernel.org/bpf/20210305094113.413544-2-bjorn.topel@gmail.com/ >
diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile index 8170f88e8ea6..f45bacbaa3d5 100644 --- a/tools/lib/bpf/Makefile +++ b/tools/lib/bpf/Makefile @@ -228,7 +228,6 @@ install_headers: $(BPF_HELPER_DEFS) $(call do_install,bpf.h,$(prefix)/include/bpf,644); \ $(call do_install,libbpf.h,$(prefix)/include/bpf,644); \ $(call do_install,btf.h,$(prefix)/include/bpf,644); \ - $(call do_install,libbpf_util.h,$(prefix)/include/bpf,644); \ $(call do_install,libbpf_common.h,$(prefix)/include/bpf,644); \ $(call do_install,xsk.h,$(prefix)/include/bpf,644); \ $(call do_install,bpf_helpers.h,$(prefix)/include/bpf,644); \ diff --git a/tools/lib/bpf/libbpf_util.h b/tools/lib/bpf/libbpf_util.h deleted file mode 100644 index 954da9b34a34..000000000000 --- a/tools/lib/bpf/libbpf_util.h +++ /dev/null @@ -1,82 +0,0 @@ -/* SPDX-License-Identifier: (LGPL-2.1 OR BSD-2-Clause) */ -/* Copyright (c) 2019 Facebook */ - -#ifndef __LIBBPF_LIBBPF_UTIL_H -#define __LIBBPF_LIBBPF_UTIL_H - -#include <stdbool.h> - -#ifdef __cplusplus -extern "C" { -#endif - -/* Load-Acquire Store-Release barriers used by the XDP socket - * library. The following macros should *NOT* be considered part of - * the xsk.h API, and is subject to change anytime. - * - * LIBRARY INTERNAL - */ - -#define __XSK_READ_ONCE(x) (*(volatile typeof(x) *)&x) -#define __XSK_WRITE_ONCE(x, v) (*(volatile typeof(x) *)&x) = (v) - -#if defined(__i386__) || defined(__x86_64__) -# define libbpf_smp_store_release(p, v) \ - do { \ - asm volatile("" : : : "memory"); \ - __XSK_WRITE_ONCE(*p, v); \ - } while (0) -# define libbpf_smp_load_acquire(p) \ - ({ \ - typeof(*p) ___p1 = __XSK_READ_ONCE(*p); \ - asm volatile("" : : : "memory"); \ - ___p1; \ - }) -#elif defined(__aarch64__) -# define libbpf_smp_store_release(p, v) \ - asm volatile ("stlr %w1, %0" : "=Q" (*p) : "r" (v) : "memory") -# define libbpf_smp_load_acquire(p) \ - ({ \ - typeof(*p) ___p1; \ - asm volatile ("ldar %w0, %1" \ - : "=r" (___p1) : "Q" (*p) : "memory"); \ - ___p1; \ - }) -#elif defined(__riscv) -# define libbpf_smp_store_release(p, v) \ - do { \ - asm volatile ("fence rw,w" : : : "memory"); \ - __XSK_WRITE_ONCE(*p, v); \ - } while (0) -# define libbpf_smp_load_acquire(p) \ - ({ \ - typeof(*p) ___p1 = __XSK_READ_ONCE(*p); \ - asm volatile ("fence r,rw" : : : "memory"); \ - ___p1; \ - }) -#endif - -#ifndef libbpf_smp_store_release -#define libbpf_smp_store_release(p, v) \ - do { \ - __sync_synchronize(); \ - __XSK_WRITE_ONCE(*p, v); \ - } while (0) -#endif - -#ifndef libbpf_smp_load_acquire -#define libbpf_smp_load_acquire(p) \ - ({ \ - typeof(*p) ___p1 = __XSK_READ_ONCE(*p); \ - __sync_synchronize(); \ - ___p1; \ - }) -#endif - -/* LIBRARY INTERNAL -- END */ - -#ifdef __cplusplus -} /* extern "C" */ -#endif - -#endif diff --git a/tools/lib/bpf/xsk.h b/tools/lib/bpf/xsk.h index a9fdea87b5cd..1d846a419d21 100644 --- a/tools/lib/bpf/xsk.h +++ b/tools/lib/bpf/xsk.h @@ -4,6 +4,7 @@ * AF_XDP user-space access library. * * Copyright(c) 2018 - 2019 Intel Corporation. + * Copyright (c) 2019 Facebook * * Author(s): Magnus Karlsson <magnus.karlsson@intel.com> */ @@ -13,15 +14,80 @@ #include <stdio.h> #include <stdint.h> +#include <stdbool.h> #include <linux/if_xdp.h> #include "libbpf.h" -#include "libbpf_util.h" #ifdef __cplusplus extern "C" { #endif +/* Load-Acquire Store-Release barriers used by the XDP socket + * library. The following macros should *NOT* be considered part of + * the xsk.h API, and is subject to change anytime. + * + * LIBRARY INTERNAL + */ + +#define __XSK_READ_ONCE(x) (*(volatile typeof(x) *)&x) +#define __XSK_WRITE_ONCE(x, v) (*(volatile typeof(x) *)&x) = (v) + +#if defined(__i386__) || defined(__x86_64__) +# define libbpf_smp_store_release(p, v) \ + do { \ + asm volatile("" : : : "memory"); \ + __XSK_WRITE_ONCE(*p, v); \ + } while (0) +# define libbpf_smp_load_acquire(p) \ + ({ \ + typeof(*p) ___p1 = __XSK_READ_ONCE(*p); \ + asm volatile("" : : : "memory"); \ + ___p1; \ + }) +#elif defined(__aarch64__) +# define libbpf_smp_store_release(p, v) \ + asm volatile ("stlr %w1, %0" : "=Q" (*p) : "r" (v) : "memory") +# define libbpf_smp_load_acquire(p) \ + ({ \ + typeof(*p) ___p1; \ + asm volatile ("ldar %w0, %1" \ + : "=r" (___p1) : "Q" (*p) : "memory"); \ + ___p1; \ + }) +#elif defined(__riscv) +# define libbpf_smp_store_release(p, v) \ + do { \ + asm volatile ("fence rw,w" : : : "memory"); \ + __XSK_WRITE_ONCE(*p, v); \ + } while (0) +# define libbpf_smp_load_acquire(p) \ + ({ \ + typeof(*p) ___p1 = __XSK_READ_ONCE(*p); \ + asm volatile ("fence r,rw" : : : "memory"); \ + ___p1; \ + }) +#endif + +#ifndef libbpf_smp_store_release +#define libbpf_smp_store_release(p, v) \ + do { \ + __sync_synchronize(); \ + __XSK_WRITE_ONCE(*p, v); \ + } while (0) +#endif + +#ifndef libbpf_smp_load_acquire +#define libbpf_smp_load_acquire(p) \ + ({ \ + typeof(*p) ___p1 = __XSK_READ_ONCE(*p); \ + __sync_synchronize(); \ + ___p1; \ + }) +#endif + +/* LIBRARY INTERNAL -- END */ + /* Do not access these members directly. Use the functions below. */ #define DEFINE_XSK_RING(name) \ struct name { \