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Say in entropy-timers.c that the AMD APERF timer is for bare metal only

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kaleb-himes
2026-10-15 08:30:40 -06:00
committed by Paul Adelsbach
parent 446024821a
commit d92f339a0d
1 changed files with 5 additions and 1 deletions
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6
wolfcrypt/src/entropy-timers.c
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@@ -28,8 +28,12 @@
#include <wolfssl/wolfcrypt/entropy-timers.h>
#include <cpuid.h>
/* Bare metal only: hypervisors trap RDPRU (AWS c7a: 881 ns a read, not 5 ns),
* so a seed takes ~1.2 s in a VM; use --enable-amdrdseed there. Details: fips
* repo entropy/portable-timer-callbacks/README.md. */
/* AMD64 APM vol. 3: RDPRU is CPUID Fn8000_0008 EBX bit 4 and RDTSCP is
* Fn8000_0001 EDX bit 27. Those leaves are vendor defined, so check AMD first. */
* Fn8000_0001 EDX bit 27. Those leaves are vendor defined: check AMD first. */
static int Entropy_AmdRdpruPresent(void)
{
unsigned int eax = 0, ebx = 0, ecx = 0, edx = 0;