Re: [dpdk-dev] [RFC] hash: unify crc32 API header for x86 and ARM

[Pavan Nikhilesh Bhagavatula <pbhagavatula@marvell.com>]

>> >> From: Pavan Nikhilesh <pbhagavatula@marvell.com>
>> >>
>> >> Merge crc32 hash calculation public API headers for x86 and ARM,
>> >> split implementations of x86 and ARM into their respective private
>> >> headers.
>> >> This reduces the ifdef code clutter while keeping current ABI
>intact.
>> >>
>> >> Although we install `rte_crc_arm64.h` it is not used in any of the lib
>or
>> >> drivers layers. All the libs and drivers use `rte_hash_crc.h` which
>falls
>> >> back to SW crc32 calculation for ARM platform.
>> >>
>> >> Signed-off-by: Pavan Nikhilesh <pbhagavatula@marvell.com>
>> >> ---
>> >>
>> >>  Currently, if application incorrectly sets CRC32_ARM64 as crc32
>> >algorithm
>> >>  through `rte_hash_crc_set_alg()` on x86 or vice-versa we fallback
>to
>> >algorithm
>> >>  set previously via `rte_hash_crc_set_alg()` instead of setting the
>best
>> >>  available.
>> >>  This behaviour should probably change to setting the best
>available
>> >algorithm
>> >>  and is up for discussion.
>> >>
>> >>  app/test/test_hash.c            |   6 +
>> >>  lib/librte_hash/Makefile        |   5 -
>> >>  lib/librte_hash/crc_arm64.h     |  67 +++++++++++
>> >>  lib/librte_hash/crc_x86.h       |  68 +++++++++++
>> >>  lib/librte_hash/meson.build     |   3 +-
>> >>  lib/librte_hash/rte_crc_arm64.h | 183 ------------------------------
>> >>  lib/librte_hash/rte_hash_crc.h  | 193 +++++++++++++--------------
>----
>> >-
>> >>  7 files changed, 219 insertions(+), 306 deletions(-)
>> >>  create mode 100644 lib/librte_hash/crc_arm64.h
>> >>  create mode 100644 lib/librte_hash/crc_x86.h
>> >>  delete mode 100644 lib/librte_hash/rte_crc_arm64.h
>> >>
>> >> diff --git a/app/test/test_hash.c b/app/test/test_hash.c
>> >> index afa3a1a3c..7bd457dac 100644
>> >> --- a/app/test/test_hash.c
>> >> +++ b/app/test/test_hash.c
>> >> @@ -195,7 +195,13 @@ test_crc32_hash_alg_equiv(void)
>> >>  	}
>> >>
>> >>  	/* Resetting to best available algorithm */
>> >> +#if defined RTE_ARCH_X86
>> >>  	rte_hash_crc_set_alg(CRC32_SSE42_x64);
>> >> +#elif defined RTE_ARCH_ARM64
>> >> +	rte_hash_crc_set_alg(CRC32_ARM64);
>> >> +#else
>> >> +	rte_hash_crc_set_alg(CRC32_SW);
>> >> +#endif
>> >>
>> >>  	if (i == CRC32_ITERATIONS)
>> >>  		return 0;
>> >> diff --git a/lib/librte_hash/Makefile b/lib/librte_hash/Makefile
>> >> index ec9f86499..f640afc42 100644
>> >> --- a/lib/librte_hash/Makefile
>> >> +++ b/lib/librte_hash/Makefile
>> >> @@ -19,11 +19,6 @@ SRCS-$(CONFIG_RTE_LIBRTE_HASH) +=
>> >rte_fbk_hash.c
>> >>  # install this header file
>> >>  SYMLINK-$(CONFIG_RTE_LIBRTE_HASH)-include := rte_hash.h
>> >>  SYMLINK-$(CONFIG_RTE_LIBRTE_HASH)-include +=
>rte_hash_crc.h
>> >> -ifeq ($(CONFIG_RTE_ARCH_ARM64),y)
>> >> -ifneq ($(findstring RTE_MACHINE_CPUFLAG_CRC32,$(CFLAGS)),)
>> >> -SYMLINK-$(CONFIG_RTE_LIBRTE_HASH)-include +=
>rte_crc_arm64.h
>> >> -endif
>> >> -endif
>> >>  SYMLINK-$(CONFIG_RTE_LIBRTE_HASH)-include += rte_jhash.h
>> >>  SYMLINK-$(CONFIG_RTE_LIBRTE_HASH)-include += rte_thash.h
>> >>  SYMLINK-$(CONFIG_RTE_LIBRTE_HASH)-include +=
>rte_fbk_hash.h
>> >> diff --git a/lib/librte_hash/crc_arm64.h
>b/lib/librte_hash/crc_arm64.h
>> >> new file mode 100644
>> >> index 000000000..8e75f8297
>> >
>> >Wouldn't that break 'make  install T=...'?
>>
>> My bad I verified with meson and it was building fine.
>>
>> >As now rte_hash_crc.h includes not public headers (crc_x86.h, etc.).
>> >Same question about external apps, where they would get from
>these
>> >headers?
>>
>> I think in the next version we can directly have the arch specific
>functions
>> Implemented in rte_hash_crc.h. Since its pretty stable code and
>overhead of extra
>> ~120 lines.
>
>Ok... but why not then just leave arch specific headers, as they are right
>now?
>What is wrong with current approach?

The problem is if any application directly includes only rte_crc_arm64.h 
(completely legal) it will break the build.

Example:

diff --git a/lib/librte_efd/rte_efd.c b/lib/librte_efd/rte_efd.c
index 6a799556d..318670940 100644
--- a/lib/librte_efd/rte_efd.c
+++ b/lib/librte_efd/rte_efd.c
@@ -19,7 +19,7 @@
 #include <rte_memcpy.h>
 #include <rte_ring.h>
 #include <rte_jhash.h>
-#include <rte_hash_crc.h>
+#include <rte_crc_arm64.h>
 #include <rte_tailq.h>

 #include "rte_efd.h"
(END)

Causes:

../lib/librte_hash/rte_crc_arm64.h: In function 'rte_hash_crc_set_alg':
../lib/librte_hash/rte_crc_arm64.h:77:7: error: 'CRC32_ARM64' undeclared (first use in this function)
   77 |  case CRC32_ARM64:
      |       ^~~~~~~~~~~
../lib/librte_hash/rte_crc_arm64.h:77:7: note: each undeclared identifier is reported only once for each function it appears in
../lib/librte_hash/rte_crc_arm64.h:79:10: error: 'CRC32_SW' undeclared (first use in this function)
   79 |    alg = CRC32_SW;
      |          ^~~~~~~~
../lib/librte_hash/rte_crc_arm64.h:82:3: error: 'crc32_alg' undeclared (first use in this function)
   82 |   crc32_alg = alg;
      |   ^~~~~~~~~
../lib/librte_hash/rte_crc_arm64.h: In function 'rte_hash_crc_init_alg':
../lib/librte_hash/rte_crc_arm64.h:92:23: error: 'CRC32_ARM64' undeclared (first use in this function)
   92 |  rte_hash_crc_set_alg(CRC32_ARM64);

Thanks,
Pavan.