20260821-linuxkm-WC_SVR_USE_NATIVE_REG_BUFS

[douzzer]

linuxkm/x86_vector_register_glue.c: add WC_SVR_USE_NATIVE_REG_BUFS: per-CPU
native vector register save buffers, serving hardirq and softirq contexts
where kernel_fpu_begin() is unusable.

previously these contexts were refused (WC_ACCEL_INHIBIT_E): hardirq
outright, softirq whenever !may_use_simd() (pre-6.15, a softirq
interrupting a foreign kernel_fpu section). an exact save/compute/restore
cycle is invisible to the interrupted context and to kernel FPU
bookkeeping, and run-to-completion freezes the blocking condition beneath
the section, so both classes are natively serviceable.

• per-CPU {softirq, hardirq} state, each {depth, pin_preempt, save_area};
  xsave64/xrstor64 with RFBM 0xe7 & XCR0 (fxsave64 fallback), plain XSAVE
  only; feature detection by direct CPUID/XGETBV, independent of kernel
  cpufeature machinery.

• recursion is a per-(CPU, class) depth count -- save on the 0->1 edge,
  restore on 1->0; softirq sections hold preempt_disable() (load-bearing
  on PREEMPT_RT).

• hardirq serves plain saves; softirq serves plain and _MAYBE_INHIBIT
  (its legacy short-circuit is bypassed when native is ready); _INHIBIT,
  hardirq _MAYBE, and NMI keep refusal semantics; task context is
  untouched.

• wc_svr_native_init() activates in place from
  wc_linuxkm_allocate_svr_states() in any context but NMI -- the FIPS
  pre-Init lazy allocation arrives inside the outermost save's own
  bracket, and wolfCrypt_Init() has been observed with irqs disabled. a
  self-bracketed register round-trip selftest gates wc_svr_native_ready;
  on any failure the long-standing refusal semantics remain fully in
  force.

• wc_linuxkm_svr_native_is_ready(): runtime readiness accessor for policy
  decisions elsewhere (e.g. the FIPS<v7 default-bank NO_VECTOR_OPS pin).

• WOLFSSL_LINUXKM_VERBOSE_DEBUG: split the softirq WC_ACCEL_INHIBIT_E
  counter into per-class counters (softirq, hardirq, NMI, other),
  reported at module shutdown.

in non-VERBOSE builds with WC_SVR_DONT_USE_NATIVE_REG_BUFS (or in non-SVR
builds), generated object code is byte-identical to the previous revision.

also add linuxkm/simd_hammer/, a stress testing tool for kernel FPU/SIMD context handling.

tested with

wolfssl-multi-test.sh ...
check-source-text
'.*dev.*cust-kern.*'
'linuxkm-legacy-.*'
quantum-safe-wolfssl-all-crypto-only-intelasm-sp-asm-sp-fips-dev-linuxkm-next-insmod
quantum-safe-wolfssl-all-crypto-only-intelasm-sp-asm-fips-dev-linuxkm-next-clang-tidy

[github-actions]

MemBrowse Memory Report

linuxkm-pie

• Data: __patchable_function_entries +56 B (+0.2%, 26,744 B)

linuxkm-standard

• Data: __patchable_function_entries +56 B (+0.1%, 49,552 B)
  No memory changes detected for:
• gcc-arm-cortex-m0plus
• gcc-arm-cortex-m3
• gcc-arm-cortex-m4
• gcc-arm-cortex-m4-baremetal
• gcc-arm-cortex-m4-crypto-only
• gcc-arm-cortex-m4-dtls13
• gcc-arm-cortex-m4-min-ecc
• gcc-arm-cortex-m4-openssl-compat
• gcc-arm-cortex-m4-pkcs7
• gcc-arm-cortex-m4-pq
• gcc-arm-cortex-m4-rsa-only
• gcc-arm-cortex-m4-sp-math
• gcc-arm-cortex-m4-tls12
• gcc-arm-cortex-m4-tls13
• gcc-arm-cortex-m7
• gcc-arm-cortex-m7-pq
• gcc-arm-cortex-m7-tls13
• stm32-sim-stm32h753

[douzzer]

retest this please
(no logs)