Author: sephe
Date: Mon May 30 08:25:09 2016
New Revision: 300987
URL: https://svnweb.freebsd.org/changeset/base/300987
Log:
hyperv/et: Fix STIMER0 operations.
- Make sure that STIMER0 is disabled before writting to it, since
writing to an enabled STIMER will result in undefined behaviour.
- It is unnecessary to reconfigure STIMER0 upon each et_start().
- Make sure that MSR_HV_REF_TIME_COUNT will not return 0, since
writing 0 to STIMER_COUNT will disable the target STIMER.
MFC after: 1 week
Sponsored by: Microsoft OSTC
Differential Revision: https://reviews.freebsd.org/D6573
Modified:
head/sys/dev/hyperv/vmbus/hv_et.c
Modified: head/sys/dev/hyperv/vmbus/hv_et.c
==============================================================================
--- head/sys/dev/hyperv/vmbus/hv_et.c Mon May 30 07:50:57 2016
(r300986)
+++ head/sys/dev/hyperv/vmbus/hv_et.c Mon May 30 08:25:09 2016
(r300987)
@@ -61,40 +61,27 @@ __FBSDID("$FreeBSD$");
static struct eventtimer *et;
-static inline uint64_t
+static __inline uint64_t
sbintime2tick(sbintime_t time)
{
struct timespec val;
val = sbttots(time);
- return val.tv_sec * HV_TIMER_FREQUENCY + val.tv_nsec / 100;
+ return (val.tv_sec * HV_TIMER_FREQUENCY) + (val.tv_nsec / 100);
}
static int
hv_et_start(struct eventtimer *et, sbintime_t firsttime, sbintime_t periodtime)
{
- uint64_t current, config;
-
- config = MSR_HV_STIMER_CFG_AUTOEN | MSR_HV_STIMER0_CFG_SINT;
+ uint64_t current;
current = rdmsr(MSR_HV_TIME_REF_COUNT);
current += sbintime2tick(firsttime);
-
- wrmsr(MSR_HV_STIMER0_CONFIG, config);
wrmsr(MSR_HV_STIMER0_COUNT, current);
return (0);
}
-static int
-hv_et_stop(struct eventtimer *et)
-{
- wrmsr(MSR_HV_STIMER0_CONFIG, 0);
- wrmsr(MSR_HV_STIMER0_COUNT, 0);
-
- return (0);
-}
-
void
hv_et_intr(struct trapframe *frame)
{
@@ -130,6 +117,31 @@ hv_et_probe(device_t dev)
return (BUS_PROBE_NOWILDCARD);
}
+static void
+vmbus_et_config(void *arg __unused)
+{
+ /*
+ * Make sure that STIMER0 is really disabled before writing
+ * to STIMER0_CONFIG.
+ *
+ * "Writing to the configuration register of a timer that
+ * is already enabled may result in undefined behaviour."
+ */
+ for (;;) {
+ uint64_t val;
+
+ /* Stop counting, and this also implies disabling STIMER0 */
+ wrmsr(MSR_HV_STIMER0_COUNT, 0);
+
+ val = rdmsr(MSR_HV_STIMER0_CONFIG);
+ if ((val & MSR_HV_STIMER_CFG_ENABLE) == 0)
+ break;
+ cpu_spinwait();
+ }
+ wrmsr(MSR_HV_STIMER0_CONFIG,
+ MSR_HV_STIMER_CFG_AUTOEN | MSR_HV_STIMER0_CFG_SINT);
+}
+
static int
hv_et_attach(device_t dev)
{
@@ -143,9 +155,16 @@ hv_et_attach(device_t dev)
et->et_min_period = HV_MIN_DELTA_TICKS * ((1LL << 32) /
HV_TIMER_FREQUENCY);
et->et_max_period = HV_MAX_DELTA_TICKS * ((1LL << 32) /
HV_TIMER_FREQUENCY);
et->et_start = hv_et_start;
- et->et_stop = hv_et_stop;
et->et_priv = dev;
+ /*
+ * Delay a bit to make sure that MSR_HV_TIME_REF_COUNT will
+ * not return 0, since writing 0 to STIMER0_COUNT will disable
+ * STIMER0.
+ */
+ DELAY(100);
+ smp_rendezvous(NULL, vmbus_et_config, NULL, NULL);
+
return (et_register(et));
}
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