KVM: x86: notifier for clocksource changes
Register a notifier for clocksource change event. In case
the host switches to clock other than TSC, disable master
clock usage.
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 1155059..c077b81 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -46,6 +46,8 @@
#include <linux/uaccess.h>
#include <linux/hash.h>
#include <linux/pci.h>
+#include <linux/timekeeper_internal.h>
+#include <linux/pvclock_gtod.h>
#include <trace/events/kvm.h>
#define CREATE_TRACE_POINTS
@@ -901,6 +903,55 @@
return kvm_set_msr(vcpu, index, *data);
}
+#ifdef CONFIG_X86_64
+struct pvclock_gtod_data {
+ seqcount_t seq;
+
+ struct { /* extract of a clocksource struct */
+ int vclock_mode;
+ cycle_t cycle_last;
+ cycle_t mask;
+ u32 mult;
+ u32 shift;
+ } clock;
+
+ /* open coded 'struct timespec' */
+ u64 monotonic_time_snsec;
+ time_t monotonic_time_sec;
+};
+
+static struct pvclock_gtod_data pvclock_gtod_data;
+
+static void update_pvclock_gtod(struct timekeeper *tk)
+{
+ struct pvclock_gtod_data *vdata = &pvclock_gtod_data;
+
+ write_seqcount_begin(&vdata->seq);
+
+ /* copy pvclock gtod data */
+ vdata->clock.vclock_mode = tk->clock->archdata.vclock_mode;
+ vdata->clock.cycle_last = tk->clock->cycle_last;
+ vdata->clock.mask = tk->clock->mask;
+ vdata->clock.mult = tk->mult;
+ vdata->clock.shift = tk->shift;
+
+ vdata->monotonic_time_sec = tk->xtime_sec
+ + tk->wall_to_monotonic.tv_sec;
+ vdata->monotonic_time_snsec = tk->xtime_nsec
+ + (tk->wall_to_monotonic.tv_nsec
+ << tk->shift);
+ while (vdata->monotonic_time_snsec >=
+ (((u64)NSEC_PER_SEC) << tk->shift)) {
+ vdata->monotonic_time_snsec -=
+ ((u64)NSEC_PER_SEC) << tk->shift;
+ vdata->monotonic_time_sec++;
+ }
+
+ write_seqcount_end(&vdata->seq);
+}
+#endif
+
+
static void kvm_write_wall_clock(struct kvm *kvm, gpa_t wall_clock)
{
int version;
@@ -997,6 +1048,8 @@
return timespec_to_ns(&ts);
}
+static atomic_t kvm_guest_has_master_clock = ATOMIC_INIT(0);
+
static DEFINE_PER_CPU(unsigned long, cpu_tsc_khz);
unsigned long max_tsc_khz;
@@ -1229,7 +1282,6 @@
vcpu->last_kernel_ns = kernel_ns;
vcpu->last_guest_tsc = tsc_timestamp;
-
/*
* The interface expects us to write an even number signaling that the
* update is finished. Since the guest won't see the intermediate
@@ -4857,6 +4909,39 @@
kvm_mmu_set_mmio_spte_mask(mask);
}
+#ifdef CONFIG_X86_64
+static void pvclock_gtod_update_fn(struct work_struct *work)
+{
+}
+
+static DECLARE_WORK(pvclock_gtod_work, pvclock_gtod_update_fn);
+
+/*
+ * Notification about pvclock gtod data update.
+ */
+static int pvclock_gtod_notify(struct notifier_block *nb, unsigned long unused,
+ void *priv)
+{
+ struct pvclock_gtod_data *gtod = &pvclock_gtod_data;
+ struct timekeeper *tk = priv;
+
+ update_pvclock_gtod(tk);
+
+ /* disable master clock if host does not trust, or does not
+ * use, TSC clocksource
+ */
+ if (gtod->clock.vclock_mode != VCLOCK_TSC &&
+ atomic_read(&kvm_guest_has_master_clock) != 0)
+ queue_work(system_long_wq, &pvclock_gtod_work);
+
+ return 0;
+}
+
+static struct notifier_block pvclock_gtod_notifier = {
+ .notifier_call = pvclock_gtod_notify,
+};
+#endif
+
int kvm_arch_init(void *opaque)
{
int r;
@@ -4898,6 +4983,10 @@
host_xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK);
kvm_lapic_init();
+#ifdef CONFIG_X86_64
+ pvclock_gtod_register_notifier(&pvclock_gtod_notifier);
+#endif
+
return 0;
out:
@@ -4912,6 +5001,9 @@
cpufreq_unregister_notifier(&kvmclock_cpufreq_notifier_block,
CPUFREQ_TRANSITION_NOTIFIER);
unregister_hotcpu_notifier(&kvmclock_cpu_notifier_block);
+#ifdef CONFIG_X86_64
+ pvclock_gtod_unregister_notifier(&pvclock_gtod_notifier);
+#endif
kvm_x86_ops = NULL;
kvm_mmu_module_exit();
}
