RE: [PATCH v2] hash: fix thash gfni implementation

["Walsh, Conor" <conor.walsh@intel.com>]

> From: David Marchand <david.marchand@redhat.com>
> Sent: Tuesday 16 November 2021 13:54
> To: Medvedkin, Vladimir <vladimir.medvedkin@intel.com>
> Cc: dev <dev@dpdk.org>; Thomas Monjalon <thomas@monjalon.net>;
> Ananyev, Konstantin <konstantin.ananyev@intel.com>; Lance Richardson
> <lance.richardson@broadcom.com>; Ji@dpdk.org; Ji, Kai <kai.ji@intel.com>;
> Wang, Yipeng1 <yipeng1.wang@intel.com>; Gobriel, Sameh
> <sameh.gobriel@intel.com>; Richardson, Bruce
> <bruce.richardson@intel.com>
> Subject: Re: [PATCH v2] hash: fix thash gfni implementation
> 
> On Fri, Nov 12, 2021 at 3:17 PM Vladimir Medvedkin
> <vladimir.medvedkin@intel.com> wrote:
> >
> > 1. This patch replaces _mm512_set_epi8 with _mm512_set_epi32
> > due to the lack of support by some compilers.
> 
> Ok, it was the initial report from Lance.
> 
> > 2. This patch checks if AVX512F is supported along with GFNI.
> > This is done if the code is built on a platform that supports GFNI,
> > but does not support AVX512.
> 
> Ok.
> 
> > 3. Also this patch fixes compilation problems on 32bit arch due to
> > lack of support for _mm_extract_epi64() by implementing XOR folding
> > with _mm_extract_epi32() on 32-bit arch.
> 
> This code is under a #if defined(__GFNI__) && defined(__AVX512F__).
> 
> Does such a 32 bits processor exist, that supports AVX512 and GFNI?


Hi David,

I ran into this issue and reported it to Vladimir.
Currently when you try to cross compile main for 32-bit (e.g. with test-meson-builds.sh) its broken because of this issue, this affects our ability to test.
So in that scenario it sees that GFNI and AVX-512 are on the system but cant build because its trying to cross compile 64-bit only functions for a 32-bit build.

Thanks,
Conor.


> 
> 
> >
> > Fixes: 4fd8c4cb0de1 ("hash: add new Toeplitz hash implementation")
> > Cc: vladimir.medvedkin@intel.com
> >
> > Signed-off-by: Vladimir Medvedkin <vladimir.medvedkin@intel.com>
> > Acked-by: Lance Richardson <lance.richardson@broadcom.com>
> > Acked-by: Ji, Kai <kai.ji@intel.com>
> > ---
> >  lib/hash/rte_thash_x86_gfni.h | 44 ++++++++++++++++++++---------------
> >  1 file changed, 25 insertions(+), 19 deletions(-)
> >
> > diff --git a/lib/hash/rte_thash_x86_gfni.h b/lib/hash/rte_thash_x86_gfni.h
> > index c2889c3734..987dec4988 100644
> > --- a/lib/hash/rte_thash_x86_gfni.h
> > +++ b/lib/hash/rte_thash_x86_gfni.h
> > @@ -18,7 +18,7 @@
> >  extern "C" {
> >  #endif
> >
> > -#ifdef __GFNI__
> > +#if defined(__GFNI__) && defined(__AVX512F__)
> 
> Please update #endif comments accordingly, or remove invalid/obsolete
> comment about _GFNI_.
> 
> 
> >  #define RTE_THASH_GFNI_DEFINED
> >
> >  #define RTE_THASH_FIRST_ITER_MSK       0x0f0f0f0f0f0e0c08
> > @@ -33,7 +33,6 @@ __rte_thash_xor_reduce(__m512i xor_acc, uint32_t
> *val_1, uint32_t *val_2)
> >  {
> >         __m256i tmp_256_1, tmp_256_2;
> >         __m128i tmp128_1, tmp128_2;
> > -       uint64_t tmp_1, tmp_2;
> >
> >         tmp_256_1 = _mm512_castsi512_si256(xor_acc);
> >         tmp_256_2 = _mm512_extracti32x8_epi32(xor_acc, 1);
> > @@ -43,12 +42,24 @@ __rte_thash_xor_reduce(__m512i xor_acc,
> uint32_t *val_1, uint32_t *val_2)
> >         tmp128_2 = _mm256_extracti32x4_epi32(tmp_256_1, 1);
> >         tmp128_1 = _mm_xor_si128(tmp128_1, tmp128_2);
> >
> > +#ifdef RTE_ARCH_X86_64
> > +       uint64_t tmp_1, tmp_2;
> >         tmp_1 = _mm_extract_epi64(tmp128_1, 0);
> >         tmp_2 = _mm_extract_epi64(tmp128_1, 1);
> >         tmp_1 ^= tmp_2;
> >
> >         *val_1 = (uint32_t)tmp_1;
> >         *val_2 = (uint32_t)(tmp_1 >> 32);
> > +#else
> > +       uint32_t tmp_1, tmp_2;
> > +       tmp_1 = _mm_extract_epi32(tmp128_1, 0);
> > +       tmp_2 = _mm_extract_epi32(tmp128_1, 1);
> > +       tmp_1 ^= _mm_extract_epi32(tmp128_1, 2);
> > +       tmp_2 ^= _mm_extract_epi32(tmp128_1, 3);
> > +
> > +       *val_1 = tmp_1;
> > +       *val_2 = tmp_2;
> > +#endif
> >  }
> >
> >  __rte_internal
> > @@ -56,23 +67,18 @@ static inline __m512i
> >  __rte_thash_gfni(const uint64_t *mtrx, const uint8_t *tuple,
> >         const uint8_t *secondary_tuple, int len)
> >  {
> > -       __m512i permute_idx = _mm512_set_epi8(7, 6, 5, 4, 7, 6, 5, 4,
> > -                                               6, 5, 4, 3, 6, 5, 4, 3,
> > -                                               5, 4, 3, 2, 5, 4, 3, 2,
> > -                                               4, 3, 2, 1, 4, 3, 2, 1,
> > -                                               3, 2, 1, 0, 3, 2, 1, 0,
> > -                                               2, 1, 0, -1, 2, 1, 0, -1,
> > -                                               1, 0, -1, -2, 1, 0, -1, -2,
> > -                                               0, -1, -2, -3, 0, -1, -2, -3);
> > -
> > -       const __m512i rewind_idx = _mm512_set_epi8(0, 0, 0, 0, 0, 0, 0, 0,
> > -                                               0, 0, 0, 0, 0, 0, 0, 0,
> > -                                               0, 0, 0, 0, 0, 0, 0, 0,
> > -                                               0, 0, 0, 0, 0, 0, 0, 0,
> > -                                               0, 0, 0, 0, 0, 0, 0, 0,
> > -                                               0, 0, 0, 59, 0, 0, 0, 59,
> > -                                               0, 0, 59, 58, 0, 0, 59, 58,
> > -                                               0, 59, 58, 57, 0, 59, 58, 57);
> > +       __m512i permute_idx = _mm512_set_epi32(0x7060504, 0x7060504,
> 
> Nit: it is easier to read fully expanded 32 bits values, like
> 0x07060504 instead of 0x7060504
> Etc...
> 
> 
> > +                                               0x6050403, 0x6050403,
> > +                                               0x5040302, 0x5040302,
> > +                                               0x4030201, 0x4030201,
> > +                                               0x3020100, 0x3020100,
> > +                                               0x20100FF, 0x20100FF,
> > +                                               0x100FFFE, 0x100FFFE,
> > +                                               0xFFFEFD, 0xFFFEFD);
> > +       const __m512i rewind_idx = _mm512_set_epi32(0, 0, 0, 0, 0, 0, 0, 0,
> > +                                                       0, 0, 0x3B, 0x3B,
> > +                                                       0x3B3A, 0x3B3A,
> > +                                                       0x3B3A39, 0x3B3A39);
> >         const __mmask64 rewind_mask = RTE_THASH_REWIND_MSK;
> >         const __m512i shift_8 = _mm512_set1_epi8(8);
> >         __m512i xor_acc = _mm512_setzero_si512();
> > --
> > 2.25.1
> >
> 
> 
> --
> David Marchand