diff options
| author | Matt Delco <delco@google.com> | 2026-03-26 17:22:54 +0000 |
|---|---|---|
| committer | Alexander Ziaee <ziaee@FreeBSD.org> | 2026-03-26 19:02:06 +0000 |
| commit | c505fc1468849150f48484b225b6476d8316de57 (patch) | |
| tree | aef2dd24588af36f92bb2b2671074a599d77d93b | |
| parent | 4b16ff49bf4bf875997fe4c80a0afc0d440b7aac (diff) | |
x86: Guard clock frequency against a divide by 0
We may be running in a Virtual Machine which may not fully support
hardware performance counters. If the MPERF counter somehow ends up
at zero, return an error and fail gracefully instead of panicking.
This patch is part of Google Cloud Engine (GCE) C4-LSSD turnup.
Sponsored by: Google
Tested by: NetApp (previous)
PR: 292808
MFC after: 3 days
Co-authored-by: Aymeric Wibo <obiwac@google.com>
Co-authored-by: Jim Mattson <jmattson@google.com>
Suggested by: jrtc27 (split out this part)
Reviewed by: imp, obiwac, olce
Differential Revision: https://reviews.freebsd.org/D56056
| -rw-r--r-- | sys/x86/x86/cpu_machdep.c | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/sys/x86/x86/cpu_machdep.c b/sys/x86/x86/cpu_machdep.c index 5483fbd6dd4e..775fee97d3cd 100644 --- a/sys/x86/x86/cpu_machdep.c +++ b/sys/x86/x86/cpu_machdep.c @@ -425,6 +425,7 @@ cpu_est_clockrate(int cpu_id, uint64_t *rate) uint64_t tsc1, tsc2; uint64_t acnt, mcnt, perf; register_t reg; + int error = 0; if (pcpu_find(cpu_id) == NULL || rate == NULL) return (EINVAL); @@ -460,6 +461,11 @@ cpu_est_clockrate(int cpu_id, uint64_t *rate) acnt = rdmsr(MSR_APERF); tsc2 = rdtsc(); intr_restore(reg); + if (mcnt == 0) { + tsc_perf_stat = 0; + error = EOPNOTSUPP; + goto err; + } perf = 1000 * acnt / mcnt; *rate = (tsc2 - tsc1) * perf; } else { @@ -470,6 +476,7 @@ cpu_est_clockrate(int cpu_id, uint64_t *rate) *rate = (tsc2 - tsc1) * 1000; } +err: #ifdef SMP if (smp_cpus > 1) { thread_lock(curthread); @@ -478,7 +485,7 @@ cpu_est_clockrate(int cpu_id, uint64_t *rate) } #endif - return (0); + return (error); } /* |