The branch main has been updated by kib:
URL:
https://cgit.FreeBSD.org/src/commit/?id=9f47eeffa3cfdcb512e2011fb00fc23c7c1a7d75
commit 9f47eeffa3cfdcb512e2011fb00fc23c7c1a7d75
Author: Konstantin Belousov <k...@freebsd.org>
AuthorDate: 2021-01-21 12:53:15 +0000
Commit: Konstantin Belousov <k...@freebsd.org>
CommitDate: 2021-01-21 12:55:31 +0000
x86: switch kernel TSC timecounter to RDTSCP on AMD Zen CPUs
Reported by: many
Tested by: gallatin, mikael, rhurlin
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
---
sys/x86/x86/tsc.c | 9 +--------
1 file changed, 1 insertion(+), 8 deletions(-)
diff --git a/sys/x86/x86/tsc.c b/sys/x86/x86/tsc.c
index 85924df98312..de0a1505c2f6 100644
--- a/sys/x86/x86/tsc.c
+++ b/sys/x86/x86/tsc.c
@@ -633,19 +633,12 @@ init:
/*
* Timecounter implementation selection, top to bottom:
- * - For AMD Zens and newer, use LFENCE;RDTSC.
* - If RDTSCP is available, use RDTSCP.
* - If fence instructions are provided (SSE2), use LFENCE;RDTSC
* on Intel, and MFENCE;RDTSC on AMD.
* - For really old CPUs, just use RDTSC.
*/
- if ((cpu_vendor_id == CPU_VENDOR_AMD ||
- cpu_vendor_id == CPU_VENDOR_HYGON) &&
- CPUID_TO_FAMILY(cpu_id) >= 0x17) {
- tsc_timecounter.tc_get_timecount = shift > 0 ?
- tsc_get_timecount_low_lfence :
- tsc_get_timecount_lfence;
- } else if ((amd_feature & AMDID_RDTSCP) != 0) {
+ if ((amd_feature & AMDID_RDTSCP) != 0) {
tsc_timecounter.tc_get_timecount = shift > 0 ?
tscp_get_timecount_low : tscp_get_timecount;
} else if ((cpu_feature & CPUID_SSE2) != 0 && mp_ncpus > 1) {
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