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

["Ananyev, Konstantin" <konstantin.ananyev@intel.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.

But we can probably mark rte_crc_arm64.h as internal, and warn users not to
include it directly (same for rte_crc_x86.h and any other arch specific headers). 

> 
> 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.
> 
>