Re: [PATCH v3 2/2] zstd: use cpu_feature_enabled() for in-kernel BMI2 dispatch

[Nick Terrell]

On Tue, Sep 1, 2026 at 7:09 AM Usama Arif <usama.arif@xxxxxxxxx> wrote:
> Zstd's dynamic BMI2 implementation probes CPUID when a compression or
> decompression context is initialized, stores the result in the context,
> and tests that value at every dispatch site. In normal kernel builds this
> bypasses the x86 feature policy and uses ordinary runtime branches instead
> of allowing x86 alternatives to resolve the feature check at boot.
>
> Add ZSTD_USE_BMI2() and use it at every runtime BMI2/default selector. For
> normal x86 kernel objects, the predicate expands directly to
> cpu_feature_enabled(X86_FEATURE_BMI2). When dynamic BMI2 dispatch is not
> available it is false; other builds retain the caller-provided flag. Keep
> the existing HUF conditional layout because DYNAMIC_BMI2 also controls
> whether target-attributed variants are emitted.
>
> Add the matching ZSTD_SET_BMI2() abstraction for context initialization.
> Normal x86 kernel objects and builds without dynamic BMI2 do not cache CPU
> state. Other builds with dynamic dispatch, including preboot, retain the
> existing behavior. Keep the BMI2 members in the context structures so
> their layouts do not change, and make the accessors return zero when
> cached state is unused.
>
> Select the normal-kernel policy in zstd_deps.h. Builds which define
> __DISABLE_EXPORTS, including the x86 preboot decompressor, retain the existing
> CPUID-backed dispatch because the normal alternatives infrastructure is not
> available there.

I don't know a lot about the preboot environment, but should we consider just
dropping support for the CPUID-backed dispatch in the preboot environment?
That would cost about 10% of performance, but perhaps the simplicity
is worth it.

> A 4 KiB zstd-generic crypto_acomp benchmark in a one-vCPU KVM guest gave
> these median results:
>
>                         Before      After     Change
>   Compression      16,634 ns/op  13,394 ns/op  -19.5%
>   Decompression     3,480 ns/op     963 ns/op  -72.3%

Thanks for these patches, this is a very welcome cleanup & performance fix!

> Signed-off-by: Usama Arif <usama.arif@xxxxxxxxx>
> ---
>  lib/zstd/common/compiler.h                    | 12 ++++++++++++
>  lib/zstd/common/entropy_common.c              | 12 ++++++------
>  lib/zstd/common/fse_decompress.c              |  7 ++++---
>  lib/zstd/common/zstd_deps.h                   |  5 +++++
>  lib/zstd/compress/huf_compress.c              |  6 +++++-
>  lib/zstd/compress/zstd_compress.c             | 12 ++++++------
>  lib/zstd/compress/zstd_compress_internal.h    |  9 +++++++++
>  lib/zstd/compress/zstd_compress_sequences.c   |  8 +++++---
>  lib/zstd/compress/zstd_compress_superblock.c  |  2 +-
>  lib/zstd/decompress/huf_decompress.c          | 18 +++++++++---------
>  lib/zstd/decompress/zstd_decompress.c         |  4 +---
>  lib/zstd/decompress/zstd_decompress_block.c   | 19 +++++++------------
>  .../decompress/zstd_decompress_internal.h     |  2 +-
>  13 files changed, 71 insertions(+), 45 deletions(-)
>
> diff --git a/lib/zstd/common/compiler.h b/lib/zstd/common/compiler.h
> index dc9bd15e174e9..47f6c0372c58c 100644
> --- a/lib/zstd/common/compiler.h
> +++ b/lib/zstd/common/compiler.h
> @@ -14,6 +14,7 @@
>
>  #include <linux/types.h>
>
> +#include "zstd_deps.h"
>  #include "portability_macros.h"
>
>  /*-*******************************************************
> @@ -96,6 +97,17 @@
>   */
>  #define BMI2_TARGET_ATTRIBUTE TARGET_ATTRIBUTE("lzcnt,bmi,bmi2")
>
> +#if !DYNAMIC_BMI2
> +#  define ZSTD_USE_BMI2(bmi2) 0
> +#  define ZSTD_SET_BMI2(state, value) do { } while (0)
> +#elif defined(ZSTD_USE_KERNEL_CPU_FEATURES)
> +#  define ZSTD_USE_BMI2(bmi2) cpu_feature_enabled(X86_FEATURE_BMI2)
> +#  define ZSTD_SET_BMI2(state, value) do { } while (0)
> +#else
> +#  define ZSTD_USE_BMI2(bmi2) (bmi2)
> +#  define ZSTD_SET_BMI2(state, value) do { (state) = (value); } while (0)
> +#endif
> +
>  /* prefetch
>   * can be disabled, by declaring NO_PREFETCH build macro */
>  #if ( (__GNUC__ >= 4) || ( (__GNUC__ == 3) && (__GNUC_MINOR__ >= 1) ) )
> diff --git a/lib/zstd/common/entropy_common.c b/lib/zstd/common/entropy_common.c
> index 15a7c14ae8040..701bd495b13c8 100644
> --- a/lib/zstd/common/entropy_common.c
> +++ b/lib/zstd/common/entropy_common.c
> @@ -16,6 +16,10 @@
>  /* *************************************
>  *  Dependencies
>  ***************************************/
> +#include "zstd_deps.h"
> +#if defined(ZSTD_USE_KERNEL_CPU_FEATURES)
> +#include <asm/cpufeature.h>
> +#endif
>  #include "mem.h"
>  #include "error_private.h"       /* ERR_*, ERROR */
>  #define FSE_STATIC_LINKING_ONLY  /* FSE_MIN_TABLELOG */
> @@ -210,11 +214,9 @@ size_t FSE_readNCount_bmi2(
>          short* normalizedCounter, unsigned* maxSVPtr, unsigned* tableLogPtr,
>          const void* headerBuffer, size_t hbSize, int bmi2)
>  {
> -#if DYNAMIC_BMI2
> -    if (bmi2) {
> +    if (ZSTD_USE_BMI2(bmi2)) {
>          return FSE_readNCount_body_bmi2(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);
>      }
> -#endif
>      (void)bmi2;
>      return FSE_readNCount_body_default(normalizedCounter, maxSVPtr, tableLogPtr, headerBuffer, hbSize);
>  }
> @@ -335,11 +337,9 @@ size_t HUF_readStats_wksp(BYTE* huffWeight, size_t hwSize, U32* rankStats,
>                       void* workSpace, size_t wkspSize,
>                       int flags)
>  {
> -#if DYNAMIC_BMI2
> -    if (flags & HUF_flags_bmi2) {
> +    if (ZSTD_USE_BMI2(flags & HUF_flags_bmi2)) {
>          return HUF_readStats_body_bmi2(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize);
>      }
> -#endif
>      (void)flags;
>      return HUF_readStats_body_default(huffWeight, hwSize, rankStats, nbSymbolsPtr, tableLogPtr, src, srcSize, workSpace, wkspSize);
>  }
> diff --git a/lib/zstd/common/fse_decompress.c b/lib/zstd/common/fse_decompress.c
> index 8d9c43b928833..008ce3401726a 100644
> --- a/lib/zstd/common/fse_decompress.c
> +++ b/lib/zstd/common/fse_decompress.c
> @@ -24,6 +24,9 @@
>  #include "fse.h"
>  #include "error_private.h"
>  #include "zstd_deps.h"  /* ZSTD_memcpy */
> +#if defined(ZSTD_USE_KERNEL_CPU_FEATURES)
> +#include <asm/cpufeature.h>
> +#endif
>  #include "bits.h"       /* ZSTD_highbit32 */
>
>
> @@ -306,11 +309,9 @@ BMI2_TARGET_ATTRIBUTE static size_t FSE_decompress_wksp_body_bmi2(void* dst, siz
>
>  size_t FSE_decompress_wksp_bmi2(void* dst, size_t dstCapacity, const void* cSrc, size_t cSrcSize, unsigned maxLog, void* workSpace, size_t wkspSize, int bmi2)
>  {
> -#if DYNAMIC_BMI2
> -    if (bmi2) {
> +    if (ZSTD_USE_BMI2(bmi2)) {
>          return FSE_decompress_wksp_body_bmi2(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize);
>      }
> -#endif
>      (void)bmi2;
>      return FSE_decompress_wksp_body_default(dst, dstCapacity, cSrc, cSrcSize, maxLog, workSpace, wkspSize);
>  }
> diff --git a/lib/zstd/common/zstd_deps.h b/lib/zstd/common/zstd_deps.h
> index f931f7d0e2947..a312029df5660 100644
> --- a/lib/zstd/common/zstd_deps.h
> +++ b/lib/zstd/common/zstd_deps.h
> @@ -26,6 +26,11 @@
>  #ifndef ZSTD_DEPS_COMMON
>  #define ZSTD_DEPS_COMMON
>
> +#if defined(__KERNEL__) && defined(CONFIG_X86) && \
> +    !defined(__DISABLE_EXPORTS)
> +#define ZSTD_USE_KERNEL_CPU_FEATURES
> +#endif
> +
>  #include <linux/limits.h>
>  #include <linux/stddef.h>
>
> diff --git a/lib/zstd/compress/huf_compress.c b/lib/zstd/compress/huf_compress.c
> index 0b229f5d2ae22..f3f53240c981d 100644
> --- a/lib/zstd/compress/huf_compress.c
> +++ b/lib/zstd/compress/huf_compress.c
> @@ -22,6 +22,9 @@
>  *  Includes
>  ****************************************************************/
>  #include "../common/zstd_deps.h"     /* ZSTD_memcpy, ZSTD_memset */
> +#if defined(ZSTD_USE_KERNEL_CPU_FEATURES)
> +#include <asm/cpufeature.h>
> +#endif
>  #include "../common/compiler.h"
>  #include "../common/bitstream.h"
>  #include "hist.h"
> @@ -1138,9 +1141,10 @@ HUF_compress1X_usingCTable_internal(void* dst, size_t dstSize,
>                                const void* src, size_t srcSize,
>                                const HUF_CElt* CTable, const int flags)
>  {
> -    if (flags & HUF_flags_bmi2) {
> +    if (ZSTD_USE_BMI2(flags & HUF_flags_bmi2)) {
>          return HUF_compress1X_usingCTable_internal_bmi2(dst, dstSize, src, srcSize, CTable);
>      }
> +    (void)flags;
>      return HUF_compress1X_usingCTable_internal_default(dst, dstSize, src, srcSize, CTable);
>  }
>
> diff --git a/lib/zstd/compress/zstd_compress.c b/lib/zstd/compress/zstd_compress.c
> index c41a747413e01..638bc0bf83127 100644
> --- a/lib/zstd/compress/zstd_compress.c
> +++ b/lib/zstd/compress/zstd_compress.c
> @@ -102,7 +102,7 @@ static void ZSTD_initCCtx(ZSTD_CCtx* cctx, ZSTD_customMem memManager)
>      assert(cctx != NULL);
>      ZSTD_memset(cctx, 0, sizeof(*cctx));
>      cctx->customMem = memManager;
> -    cctx->bmi2 = ZSTD_cpuSupportsBmi2();
> +    ZSTD_SET_BMI2(cctx->bmi2, ZSTD_cpuSupportsBmi2());
>      {   size_t const err = ZSTD_CCtx_reset(cctx, ZSTD_reset_parameters);
>          assert(!ZSTD_isError(err));
>          (void)err;
> @@ -142,7 +142,7 @@ ZSTD_CCtx* ZSTD_initStaticCCtx(void* workspace, size_t workspaceSize)
>      cctx->blockState.nextCBlock = (ZSTD_compressedBlockState_t*)ZSTD_cwksp_reserve_object(&cctx->workspace, sizeof(ZSTD_compressedBlockState_t));
>      cctx->tmpWorkspace = ZSTD_cwksp_reserve_object(&cctx->workspace, TMP_WORKSPACE_SIZE);
>      cctx->tmpWkspSize = TMP_WORKSPACE_SIZE;
> -    cctx->bmi2 = ZSTD_cpuid_bmi2(ZSTD_cpuid());
> +    ZSTD_SET_BMI2(cctx->bmi2, ZSTD_cpuid_bmi2(ZSTD_cpuid()));
>      return cctx;
>  }
>
> @@ -4042,7 +4042,7 @@ ZSTD_compressSeqStore_singleBlock(ZSTD_CCtx* zc,
>                  op + ZSTD_blockHeaderSize, dstCapacity - ZSTD_blockHeaderSize,
>                  srcSize,
>                  zc->tmpWorkspace, zc->tmpWkspSize /* statically allocated in resetCCtx */,
> -                zc->bmi2);
> +                ZSTD_CCtx_get_bmi2(zc));
>      FORWARD_IF_ERROR(cSeqsSize, "ZSTD_entropyCompressSeqStore failed!");
>
>      if (!zc->isFirstBlock &&
> @@ -4332,7 +4332,7 @@ ZSTD_compressBlock_internal(ZSTD_CCtx* zc,
>              dst, dstCapacity,
>              srcSize,
>              zc->tmpWorkspace, zc->tmpWkspSize /* statically allocated in resetCCtx */,
> -            zc->bmi2);
> +            ZSTD_CCtx_get_bmi2(zc));
>
>      if (frame &&
>          /* We don't want to emit our first block as a RLE even if it qualifies because
> @@ -6796,7 +6796,7 @@ ZSTD_compressSequences_internal(ZSTD_CCtx* cctx,
>                                  op + ZSTD_blockHeaderSize /* Leave space for block header */, dstCapacity - ZSTD_blockHeaderSize,
>                                  blockSize,
>                                  cctx->tmpWorkspace, cctx->tmpWkspSize /* statically allocated in resetCCtx */,
> -                                cctx->bmi2);
> +                                ZSTD_CCtx_get_bmi2(cctx));
>          FORWARD_IF_ERROR(compressedSeqsSize, "Compressing sequences of block failed");
>          DEBUGLOG(5, "Compressed sequences size: %zu", compressedSeqsSize);
>
> @@ -7321,7 +7321,7 @@ ZSTD_compressSequencesAndLiterals_internal(ZSTD_CCtx* cctx,
>                                  &cctx->blockState.prevCBlock->entropy, &cctx->blockState.nextCBlock->entropy,
>                                  &cctx->appliedParams,
>                                  cctx->tmpWorkspace, cctx->tmpWkspSize /* statically allocated in resetCCtx */,
> -                                cctx->bmi2);
> +                                ZSTD_CCtx_get_bmi2(cctx));
>          FORWARD_IF_ERROR(compressedSeqsSize, "Compressing sequences of block failed");
>          /* note: the spec forbids for any compressed block to be larger than maximum block size */
>          if (compressedSeqsSize > cctx->blockSizeMax) compressedSeqsSize = 0;
> diff --git a/lib/zstd/compress/zstd_compress_internal.h b/lib/zstd/compress/zstd_compress_internal.h
> index b109783858763..99ebe1e0c923f 100644
> --- a/lib/zstd/compress/zstd_compress_internal.h
> +++ b/lib/zstd/compress/zstd_compress_internal.h
> @@ -537,6 +537,15 @@ struct ZSTD_CCtx_s {
>      size_t extSeqBufCapacity;
>  };
>
> +MEM_STATIC int ZSTD_CCtx_get_bmi2(const struct ZSTD_CCtx_s *cctx) {
> +#if DYNAMIC_BMI2 && !defined(ZSTD_USE_KERNEL_CPU_FEATURES)
> +    return cctx->bmi2;
> +#else
> +    (void)cctx;
> +    return 0;
> +#endif
> +}
> +
>  typedef enum { ZSTD_dtlm_fast, ZSTD_dtlm_full } ZSTD_dictTableLoadMethod_e;
>  typedef enum { ZSTD_tfp_forCCtx, ZSTD_tfp_forCDict } ZSTD_tableFillPurpose_e;
>
> diff --git a/lib/zstd/compress/zstd_compress_sequences.c b/lib/zstd/compress/zstd_compress_sequences.c
> index 64abcdf2c5714..7a03a8fceea7d 100644
> --- a/lib/zstd/compress/zstd_compress_sequences.c
> +++ b/lib/zstd/compress/zstd_compress_sequences.c
> @@ -12,6 +12,10 @@
>   /*-*************************************
>   *  Dependencies
>   ***************************************/
> +#include "../common/zstd_deps.h"
> +#if defined(ZSTD_USE_KERNEL_CPU_FEATURES)
> +#include <asm/cpufeature.h>
> +#endif
>  #include "zstd_compress_sequences.h"
>
>  /*
> @@ -429,15 +433,13 @@ size_t ZSTD_encodeSequences(
>              SeqDef const* sequences, size_t nbSeq, int longOffsets, int bmi2)
>  {
>      DEBUGLOG(5, "ZSTD_encodeSequences: dstCapacity = %u", (unsigned)dstCapacity);
> -#if DYNAMIC_BMI2
> -    if (bmi2) {
> +    if (ZSTD_USE_BMI2(bmi2)) {
>          return ZSTD_encodeSequences_bmi2(dst, dstCapacity,
>                                           CTable_MatchLength, mlCodeTable,
>                                           CTable_OffsetBits, ofCodeTable,
>                                           CTable_LitLength, llCodeTable,
>                                           sequences, nbSeq, longOffsets);
>      }
> -#endif
>      (void)bmi2;
>      return ZSTD_encodeSequences_default(dst, dstCapacity,
>                                          CTable_MatchLength, mlCodeTable,
> diff --git a/lib/zstd/compress/zstd_compress_superblock.c b/lib/zstd/compress/zstd_compress_superblock.c
> index dc12d64e935c4..fada5979c3b84 100644
> --- a/lib/zstd/compress/zstd_compress_superblock.c
> +++ b/lib/zstd/compress/zstd_compress_superblock.c
> @@ -684,6 +684,6 @@ size_t ZSTD_compressSuperBlock(ZSTD_CCtx* zc,
>              &zc->appliedParams,
>              dst, dstCapacity,
>              src, srcSize,
> -            zc->bmi2, lastBlock,
> +            ZSTD_CCtx_get_bmi2(zc), lastBlock,
>              zc->tmpWorkspace, zc->tmpWkspSize /* statically allocated in resetCCtx */);
>  }
> diff --git a/lib/zstd/decompress/huf_decompress.c b/lib/zstd/decompress/huf_decompress.c
> index 5663ae524cd83..8bf2279887e8f 100644
> --- a/lib/zstd/decompress/huf_decompress.c
> +++ b/lib/zstd/decompress/huf_decompress.c
> @@ -17,6 +17,9 @@
>  *  Dependencies
>  ****************************************************************/
>  #include "../common/zstd_deps.h"  /* ZSTD_memcpy, ZSTD_memset */
> +#if defined(ZSTD_USE_KERNEL_CPU_FEATURES)
> +#include <asm/cpufeature.h>
> +#endif
>  #include "../common/compiler.h"
>  #include "../common/bitstream.h"  /* BIT_* */
>  #include "../common/fse.h"        /* to compress headers */
> @@ -113,9 +116,10 @@ typedef size_t (*HUF_DecompressUsingDTableFn)(void *dst, size_t dstSize,
>      static size_t fn(void* dst, size_t dstSize, void const* cSrc,           \
>                       size_t cSrcSize, HUF_DTable const* DTable, int flags)  \
>      {                                                                       \
> -        if (flags & HUF_flags_bmi2) {                                       \
> +        if (ZSTD_USE_BMI2(flags & HUF_flags_bmi2)) {                        \
>              return fn##_bmi2(dst, dstSize, cSrc, cSrcSize, DTable);         \
>          }                                                                   \
> +        (void)flags;                                                        \
>          return fn##_default(dst, dstSize, cSrc, cSrcSize, DTable);          \
>      }
>
> @@ -899,18 +903,16 @@ static size_t HUF_decompress4X1_usingDTable_internal(void* dst, size_t dstSize,
>      HUF_DecompressUsingDTableFn fallbackFn = HUF_decompress4X1_usingDTable_internal_default;
>      HUF_DecompressFastLoopFn loopFn = HUF_decompress4X1_usingDTable_internal_fast_c_loop;
>
> -#if DYNAMIC_BMI2
> -    if (flags & HUF_flags_bmi2) {
> +    if (ZSTD_USE_BMI2(flags & HUF_flags_bmi2)) {
>          fallbackFn = HUF_decompress4X1_usingDTable_internal_bmi2;
>  # if ZSTD_ENABLE_ASM_X86_64_BMI2
>          if (!(flags & HUF_flags_disableAsm)) {
>              loopFn = HUF_decompress4X1_usingDTable_internal_fast_asm_loop;
>          }
>  # endif
> -    } else {
> +    } else if (DYNAMIC_BMI2) {
>          return fallbackFn(dst, dstSize, cSrc, cSrcSize, DTable);
>      }
> -#endif
>
>  #if ZSTD_ENABLE_ASM_X86_64_BMI2 && defined(__BMI2__)
>      if (!(flags & HUF_flags_disableAsm)) {
> @@ -1723,18 +1725,16 @@ static size_t HUF_decompress4X2_usingDTable_internal(void* dst, size_t dstSize,
>      HUF_DecompressUsingDTableFn fallbackFn = HUF_decompress4X2_usingDTable_internal_default;
>      HUF_DecompressFastLoopFn loopFn = HUF_decompress4X2_usingDTable_internal_fast_c_loop;
>
> -#if DYNAMIC_BMI2
> -    if (flags & HUF_flags_bmi2) {
> +    if (ZSTD_USE_BMI2(flags & HUF_flags_bmi2)) {
>          fallbackFn = HUF_decompress4X2_usingDTable_internal_bmi2;
>  # if ZSTD_ENABLE_ASM_X86_64_BMI2
>          if (!(flags & HUF_flags_disableAsm)) {
>              loopFn = HUF_decompress4X2_usingDTable_internal_fast_asm_loop;
>          }
>  # endif
> -    } else {
> +    } else if (DYNAMIC_BMI2) {
>          return fallbackFn(dst, dstSize, cSrc, cSrcSize, DTable);
>      }
> -#endif
>
>  #if ZSTD_ENABLE_ASM_X86_64_BMI2 && defined(__BMI2__)
>      if (!(flags & HUF_flags_disableAsm)) {
> diff --git a/lib/zstd/decompress/zstd_decompress.c b/lib/zstd/decompress/zstd_decompress.c
> index bb009554e3a61..cc6ecd364970a 100644
> --- a/lib/zstd/decompress/zstd_decompress.c
> +++ b/lib/zstd/decompress/zstd_decompress.c
> @@ -259,9 +259,7 @@ static void ZSTD_initDCtx_internal(ZSTD_DCtx* dctx)
>      dctx->noForwardProgress = 0;
>      dctx->oversizedDuration = 0;
>      dctx->isFrameDecompression = 1;
> -#if DYNAMIC_BMI2
> -    dctx->bmi2 = ZSTD_cpuSupportsBmi2();
> -#endif
> +    ZSTD_SET_BMI2(dctx->bmi2, ZSTD_cpuSupportsBmi2());
>      dctx->ddictSet = NULL;
>      ZSTD_DCtx_resetParameters(dctx);
>  #ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
> diff --git a/lib/zstd/decompress/zstd_decompress_block.c b/lib/zstd/decompress/zstd_decompress_block.c
> index 9c4215e435014..31804cbf1f7ed 100644
> --- a/lib/zstd/decompress/zstd_decompress_block.c
> +++ b/lib/zstd/decompress/zstd_decompress_block.c
> @@ -16,6 +16,9 @@
>  *  Dependencies
>  *********************************************************/
>  #include "../common/zstd_deps.h"   /* ZSTD_memcpy, ZSTD_memmove, ZSTD_memset */
> +#if defined(ZSTD_USE_KERNEL_CPU_FEATURES)
> +#include <asm/cpufeature.h>
> +#endif
>  #include "../common/compiler.h"    /* prefetch */
>  #include "../common/cpu.h"         /* bmi2 */
>  #include "../common/mem.h"         /* low level memory routines */
> @@ -631,13 +634,11 @@ void ZSTD_buildFSETable(ZSTD_seqSymbol* dt,
>              const U32* baseValue, const U8* nbAdditionalBits,
>              unsigned tableLog, void* wksp, size_t wkspSize, int bmi2)
>  {
> -#if DYNAMIC_BMI2
> -    if (bmi2) {
> +    if (ZSTD_USE_BMI2(bmi2)) {
>          ZSTD_buildFSETable_body_bmi2(dt, normalizedCounter, maxSymbolValue,
>                  baseValue, nbAdditionalBits, tableLog, wksp, wkspSize);
>          return;
>      }
> -#endif
>      (void)bmi2;
>      ZSTD_buildFSETable_body_default(dt, normalizedCounter, maxSymbolValue,
>              baseValue, nbAdditionalBits, tableLog, wksp, wkspSize);
> @@ -1955,11 +1956,9 @@ ZSTD_decompressSequences(ZSTD_DCtx* dctx, void* dst, size_t maxDstSize,
>                     const ZSTD_longOffset_e isLongOffset)
>  {
>      DEBUGLOG(5, "ZSTD_decompressSequences");
> -#if DYNAMIC_BMI2
> -    if (ZSTD_DCtx_get_bmi2(dctx)) {
> +    if (ZSTD_USE_BMI2(ZSTD_DCtx_get_bmi2(dctx))) {
>          return ZSTD_decompressSequences_bmi2(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset);
>      }
> -#endif
>      return ZSTD_decompressSequences_default(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset);
>  }
>  static size_t
> @@ -1968,11 +1967,9 @@ ZSTD_decompressSequencesSplitLitBuffer(ZSTD_DCtx* dctx, void* dst, size_t maxDst
>                                   const ZSTD_longOffset_e isLongOffset)
>  {
>      DEBUGLOG(5, "ZSTD_decompressSequencesSplitLitBuffer");
> -#if DYNAMIC_BMI2
> -    if (ZSTD_DCtx_get_bmi2(dctx)) {
> +    if (ZSTD_USE_BMI2(ZSTD_DCtx_get_bmi2(dctx))) {
>          return ZSTD_decompressSequencesSplitLitBuffer_bmi2(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset);
>      }
> -#endif
>      return ZSTD_decompressSequencesSplitLitBuffer_default(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset);
>  }
>  #endif /* ZSTD_FORCE_DECOMPRESS_SEQUENCES_LONG */
> @@ -1991,11 +1988,9 @@ ZSTD_decompressSequencesLong(ZSTD_DCtx* dctx,
>                               const ZSTD_longOffset_e isLongOffset)
>  {
>      DEBUGLOG(5, "ZSTD_decompressSequencesLong");
> -#if DYNAMIC_BMI2
> -    if (ZSTD_DCtx_get_bmi2(dctx)) {
> +    if (ZSTD_USE_BMI2(ZSTD_DCtx_get_bmi2(dctx))) {
>          return ZSTD_decompressSequencesLong_bmi2(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset);
>      }
> -#endif
>    return ZSTD_decompressSequencesLong_default(dctx, dst, maxDstSize, seqStart, seqSize, nbSeq, isLongOffset);
>  }
>  #endif /* ZSTD_FORCE_DECOMPRESS_SEQUENCES_SHORT */
> diff --git a/lib/zstd/decompress/zstd_decompress_internal.h b/lib/zstd/decompress/zstd_decompress_internal.h
> index 2a225d1811c4f..401f2b526bbce 100644
> --- a/lib/zstd/decompress/zstd_decompress_internal.h
> +++ b/lib/zstd/decompress/zstd_decompress_internal.h
> @@ -204,7 +204,7 @@ struct ZSTD_DCtx_s
>  };  /* typedef'd to ZSTD_DCtx within "zstd.h" */
>
>  MEM_STATIC int ZSTD_DCtx_get_bmi2(const struct ZSTD_DCtx_s *dctx) {
> -#if DYNAMIC_BMI2
> +#if DYNAMIC_BMI2 && !defined(ZSTD_USE_KERNEL_CPU_FEATURES)
>      return dctx->bmi2;
>  #else
>      (void)dctx;
> --
> 2.53.0-Meta
>