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[bpf-next,v2,07/15] selftests/xsk: replace asm acquire/release implementations

Message ID 20230104121744.2820-8-magnus.karlsson@gmail.com (mailing list archive)
State Superseded
Delegated to: BPF
Headers show
Series selftests/xsk: speed-ups, fixes, and new XDP programs | expand

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bpf/vmtest-bpf-next-PR success PR summary
netdev/tree_selection success Clearly marked for bpf-next, async
netdev/fixes_present success Fixes tag not required for -next series
netdev/subject_prefix success Link
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netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 0 this patch: 0
netdev/cc_maintainers warning 14 maintainers not CCed: linux-kselftest@vger.kernel.org trix@redhat.com paul.walmsley@sifive.com davem@davemloft.net llvm@lists.linux.dev kuba@kernel.org aou@eecs.berkeley.edu palmer@dabbelt.com nathan@kernel.org linux-riscv@lists.infradead.org ndesaulniers@google.com shuah@kernel.org hawk@kernel.org mykolal@fb.com
netdev/build_clang success Errors and warnings before: 0 this patch: 0
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
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netdev/checkpatch warning WARNING: line length of 81 exceeds 80 columns
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Commit Message

Magnus Karlsson Jan. 4, 2023, 12:17 p.m. UTC 
From: Magnus Karlsson <magnus.karlsson@intel.com>

Replace our own homegrown assembly store/release and load/acquire
implementations with the HW agnositic atomic APIs C11 offers. This to
make the code more portable, easier to read, and reduce the
maintenance burden.

The original code used load-acquire and store-release barriers
hand-coded in assembly. Since C11, these kind of operations are
offered as built-ins in gcc and llvm. The load-acquire operation
prevents hoisting of non-atomic memory operations to before this
operation and it corresponds to the __ATOMIC_ACQUIRE operation in the
built-in atomics. The store-release operation prevents hoisting of
non-atomic memory operations to after this operation and it
corresponds to the __ATOMIC_RELEASE operation in the built-in atomics.

Signed-off-by: Magnus Karlsson <magnus.karlsson@intel.com>
---
 tools/testing/selftests/bpf/xsk.h | 80 ++-----------------------------
 1 file changed, 4 insertions(+), 76 deletions(-)
diff mbox series

Patch

diff --git a/tools/testing/selftests/bpf/xsk.h b/tools/testing/selftests/bpf/xsk.h
index 997723b0bfb2..24ee765aded3 100644
--- a/tools/testing/selftests/bpf/xsk.h
+++ b/tools/testing/selftests/bpf/xsk.h
@@ -23,77 +23,6 @@ 
 extern "C" {
 #endif
 
-/* This whole API has been deprecated and moved to libxdp that can be found at
- * https://github.com/xdp-project/xdp-tools. The APIs are exactly the same so
- * it should just be linking with libxdp instead of libbpf for this set of
- * functionality. If not, please submit a bug report on the aforementioned page.
- */
-
-/* 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 { \
@@ -168,7 +97,7 @@  static inline __u32 xsk_prod_nb_free(struct xsk_ring_prod *r, __u32 nb)
 	 * this function. Without this optimization it whould have been
 	 * free_entries = r->cached_prod - r->cached_cons + r->size.
 	 */
-	r->cached_cons = libbpf_smp_load_acquire(r->consumer);
+	r->cached_cons = __atomic_load_n(r->consumer, __ATOMIC_ACQUIRE);
 	r->cached_cons += r->size;
 
 	return r->cached_cons - r->cached_prod;
@@ -179,7 +108,7 @@  static inline __u32 xsk_cons_nb_avail(struct xsk_ring_cons *r, __u32 nb)
 	__u32 entries = r->cached_prod - r->cached_cons;
 
 	if (entries == 0) {
-		r->cached_prod = libbpf_smp_load_acquire(r->producer);
+		r->cached_prod = __atomic_load_n(r->producer, __ATOMIC_ACQUIRE);
 		entries = r->cached_prod - r->cached_cons;
 	}
 
@@ -202,7 +131,7 @@  static inline void xsk_ring_prod__submit(struct xsk_ring_prod *prod, __u32 nb)
 	/* Make sure everything has been written to the ring before indicating
 	 * this to the kernel by writing the producer pointer.
 	 */
-	libbpf_smp_store_release(prod->producer, *prod->producer + nb);
+	__atomic_store_n(prod->producer, *prod->producer + nb, __ATOMIC_RELEASE);
 }
 
 static inline __u32 xsk_ring_cons__peek(struct xsk_ring_cons *cons, __u32 nb, __u32 *idx)
@@ -227,8 +156,7 @@  static inline void xsk_ring_cons__release(struct xsk_ring_cons *cons, __u32 nb)
 	/* Make sure data has been read before indicating we are done
 	 * with the entries by updating the consumer pointer.
 	 */
-	libbpf_smp_store_release(cons->consumer, *cons->consumer + nb);
-
+	__atomic_store_n(cons->consumer, *cons->consumer + nb, __ATOMIC_RELEASE);
 }
 
 static inline void *xsk_umem__get_data(void *umem_area, __u64 addr)