Author: neel
Date: Wed Apr 10 05:59:07 2013
New Revision: 249324
URL: http://svnweb.freebsd.org/changeset/base/249324
Log:
Unsynchronized TSCs on the host require special handling in bhyve:
- use clock_gettime(2) as the time base for the emulated ACPI timer instead
of directly using rdtsc().
- don't advertise the invariant TSC capability to the guest to discourage it
from using the TSC as its time base.
Discussed with: jhb@ (about making 'smp_tsc' a global)
Reported by: Dan Mack on freebsd-virtualization@
Obtained from: NetApp
Modified:
head/sys/amd64/include/clock.h
head/sys/amd64/vmm/x86.c
head/sys/x86/x86/tsc.c
head/usr.sbin/bhyve/pmtmr.c
Modified: head/sys/amd64/include/clock.h
==============================================================================
--- head/sys/amd64/include/clock.h Wed Apr 10 02:40:03 2013
(r249323)
+++ head/sys/amd64/include/clock.h Wed Apr 10 05:59:07 2013
(r249324)
@@ -20,6 +20,9 @@ extern int i8254_max_count;
extern uint64_t tsc_freq;
extern int tsc_is_invariant;
extern int tsc_perf_stat;
+#ifdef SMP
+extern int smp_tsc;
+#endif
void i8254_init(void);
Modified: head/sys/amd64/vmm/x86.c
==============================================================================
--- head/sys/amd64/vmm/x86.c Wed Apr 10 02:40:03 2013 (r249323)
+++ head/sys/amd64/vmm/x86.c Wed Apr 10 05:59:07 2013 (r249324)
@@ -34,6 +34,7 @@ __FBSDID("$FreeBSD$");
#include <sys/systm.h>
#include <sys/cpuset.h>
+#include <machine/clock.h>
#include <machine/cpufunc.h>
#include <machine/md_var.h>
#include <machine/specialreg.h>
@@ -89,11 +90,27 @@ x86_emulate_cpuid(struct vm *vm, int vcp
case CPUID_8000_0003:
case CPUID_8000_0004:
case CPUID_8000_0006:
- case CPUID_8000_0007:
case CPUID_8000_0008:
cpuid_count(*eax, *ecx, regs);
break;
+ case CPUID_8000_0007:
+ cpuid_count(*eax, *ecx, regs);
+ /*
+ * If the host TSCs are not synchronized across
+ * physical cpus then we cannot advertise an
+ * invariant tsc to a vcpu.
+ *
+ * XXX This still falls short because the vcpu
+ * can observe the TSC moving backwards as it
+ * migrates across physical cpus. But at least
+ * it should discourage the guest from using the
+ * TSC to keep track of time.
+ */
+ if (!smp_tsc)
+ regs[3] &= ~AMDPM_TSC_INVARIANT;
+ break;
+
case CPUID_0000_0001:
do_cpuid(1, regs);
Modified: head/sys/x86/x86/tsc.c
==============================================================================
--- head/sys/x86/x86/tsc.c Wed Apr 10 02:40:03 2013 (r249323)
+++ head/sys/x86/x86/tsc.c Wed Apr 10 05:59:07 2013 (r249324)
@@ -61,7 +61,7 @@ SYSCTL_INT(_kern_timecounter, OID_AUTO,
TUNABLE_INT("kern.timecounter.invariant_tsc", &tsc_is_invariant);
#ifdef SMP
-static int smp_tsc;
+int smp_tsc;
SYSCTL_INT(_kern_timecounter, OID_AUTO, smp_tsc, CTLFLAG_RDTUN, &smp_tsc, 0,
"Indicates whether the TSC is safe to use in SMP mode");
TUNABLE_INT("kern.timecounter.smp_tsc", &smp_tsc);
Modified: head/usr.sbin/bhyve/pmtmr.c
==============================================================================
--- head/usr.sbin/bhyve/pmtmr.c Wed Apr 10 02:40:03 2013 (r249323)
+++ head/usr.sbin/bhyve/pmtmr.c Wed Apr 10 05:59:07 2013 (r249324)
@@ -35,6 +35,7 @@ __FBSDID("$FreeBSD$");
#include <machine/cpufunc.h>
#include <stdio.h>
+#include <stdlib.h>
#include <time.h>
#include <assert.h>
#include <pthread.h>
@@ -53,35 +54,108 @@ __FBSDID("$FreeBSD$");
#define PMTMR_FREQ 3579545 /* 3.579545MHz */
static pthread_mutex_t pmtmr_mtx;
-static uint64_t pmtmr_tscf;
+
static uint64_t pmtmr_old;
+
+static uint64_t pmtmr_tscf;
static uint64_t pmtmr_tsc_old;
+static clockid_t clockid = CLOCK_UPTIME_FAST;
+static struct timespec pmtmr_uptime_old;
+
+#define timespecsub(vvp, uvp)
\
+ do { \
+ (vvp)->tv_sec -= (uvp)->tv_sec; \
+ (vvp)->tv_nsec -= (uvp)->tv_nsec; \
+ if ((vvp)->tv_nsec < 0) { \
+ (vvp)->tv_sec--; \
+ (vvp)->tv_nsec += 1000000000; \
+ } \
+ } while (0)
+
+static uint64_t
+timespec_to_pmtmr(const struct timespec *tsnew, const struct timespec *tsold)
+{
+ struct timespec tsdiff;
+ int64_t nsecs;
+
+ tsdiff = *tsnew;
+ timespecsub(&tsdiff, tsold);
+ nsecs = tsdiff.tv_sec * 1000000000 + tsdiff.tv_nsec;
+ assert(nsecs >= 0);
+
+ return (nsecs * PMTMR_FREQ / 1000000000 + pmtmr_old);
+}
+
+static uint64_t
+tsc_to_pmtmr(uint64_t tsc_new, uint64_t tsc_old)
+{
+
+ return ((tsc_new - tsc_old) * PMTMR_FREQ / pmtmr_tscf + pmtmr_old);
+}
+
+static void
+pmtmr_init(void)
+{
+ size_t len;
+ int smp_tsc, err;
+ struct timespec tsnew, tsold = { 0 };
+
+ len = sizeof(smp_tsc);
+ err = sysctlbyname("kern.timecounter.smp_tsc", &smp_tsc, &len, NULL, 0);
+ assert(err == 0);
+
+ if (smp_tsc) {
+ len = sizeof(pmtmr_tscf);
+ err = sysctlbyname("machdep.tsc_freq", &pmtmr_tscf, &len,
+ NULL, 0);
+ assert(err == 0);
+
+ pmtmr_tsc_old = rdtsc();
+ pmtmr_old = tsc_to_pmtmr(pmtmr_tsc_old, 0);
+ } else {
+ if (getenv("BHYVE_PMTMR_PRECISE") != NULL)
+ clockid = CLOCK_UPTIME;
+
+ err = clock_gettime(clockid, &tsnew);
+ assert(err == 0);
+
+ pmtmr_uptime_old = tsnew;
+ pmtmr_old = timespec_to_pmtmr(&tsnew, &tsold);
+ }
+}
+
static uint32_t
pmtmr_val(void)
{
+ struct timespec tsnew;
uint64_t pmtmr_tsc_new;
uint64_t pmtmr_new;
+ int error;
+
static int inited = 0;
if (!inited) {
- size_t len;
-
- inited = 1;
pthread_mutex_init(&pmtmr_mtx, NULL);
- len = sizeof(pmtmr_tscf);
- sysctlbyname("machdep.tsc_freq", &pmtmr_tscf, &len,
- NULL, 0);
- pmtmr_tsc_old = rdtsc();
- pmtmr_old = pmtmr_tsc_old / pmtmr_tscf * PMTMR_FREQ;
+ pmtmr_init();
+ inited = 1;
}
pthread_mutex_lock(&pmtmr_mtx);
- pmtmr_tsc_new = rdtsc();
- pmtmr_new = (pmtmr_tsc_new - pmtmr_tsc_old) * PMTMR_FREQ / pmtmr_tscf +
- pmtmr_old;
+
+ if (pmtmr_tscf) {
+ pmtmr_tsc_new = rdtsc();
+ pmtmr_new = tsc_to_pmtmr(pmtmr_tsc_new, pmtmr_tsc_old);
+ pmtmr_tsc_old = pmtmr_tsc_new;
+ } else {
+ error = clock_gettime(clockid, &tsnew);
+ assert(error == 0);
+
+ pmtmr_new = timespec_to_pmtmr(&tsnew, &pmtmr_uptime_old);
+ pmtmr_uptime_old = tsnew;
+ }
pmtmr_old = pmtmr_new;
- pmtmr_tsc_old = pmtmr_tsc_new;
+
pthread_mutex_unlock(&pmtmr_mtx);
return (pmtmr_new);
@@ -102,4 +176,3 @@ pmtmr_handler(struct vmctx *ctx, int vcp
}
INOUT_PORT(pmtmr, IO_PMTMR, IOPORT_F_IN, pmtmr_handler);
-
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