v4.19.13 snapshot.
diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c
new file mode 100644
index 0000000..637982e
--- /dev/null
+++ b/arch/x86/kernel/pvclock.c
@@ -0,0 +1,167 @@
+/* paravirtual clock -- common code used by kvm/xen
+
+ This program is free software; you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation; either version 2 of the License, or
+ (at your option) any later version.
+
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with this program; if not, write to the Free Software
+ Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+*/
+
+#include <linux/kernel.h>
+#include <linux/percpu.h>
+#include <linux/notifier.h>
+#include <linux/sched.h>
+#include <linux/gfp.h>
+#include <linux/bootmem.h>
+#include <linux/nmi.h>
+
+#include <asm/fixmap.h>
+#include <asm/pvclock.h>
+#include <asm/vgtod.h>
+
+static u8 valid_flags __read_mostly = 0;
+static struct pvclock_vsyscall_time_info *pvti_cpu0_va __read_mostly;
+
+void pvclock_set_flags(u8 flags)
+{
+ valid_flags = flags;
+}
+
+unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src)
+{
+ u64 pv_tsc_khz = 1000000ULL << 32;
+
+ do_div(pv_tsc_khz, src->tsc_to_system_mul);
+ if (src->tsc_shift < 0)
+ pv_tsc_khz <<= -src->tsc_shift;
+ else
+ pv_tsc_khz >>= src->tsc_shift;
+ return pv_tsc_khz;
+}
+
+void pvclock_touch_watchdogs(void)
+{
+ touch_softlockup_watchdog_sync();
+ clocksource_touch_watchdog();
+ rcu_cpu_stall_reset();
+ reset_hung_task_detector();
+}
+
+static atomic64_t last_value = ATOMIC64_INIT(0);
+
+void pvclock_resume(void)
+{
+ atomic64_set(&last_value, 0);
+}
+
+u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src)
+{
+ unsigned version;
+ u8 flags;
+
+ do {
+ version = pvclock_read_begin(src);
+ flags = src->flags;
+ } while (pvclock_read_retry(src, version));
+
+ return flags & valid_flags;
+}
+
+u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
+{
+ unsigned version;
+ u64 ret;
+ u64 last;
+ u8 flags;
+
+ do {
+ version = pvclock_read_begin(src);
+ ret = __pvclock_read_cycles(src, rdtsc_ordered());
+ flags = src->flags;
+ } while (pvclock_read_retry(src, version));
+
+ if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) {
+ src->flags &= ~PVCLOCK_GUEST_STOPPED;
+ pvclock_touch_watchdogs();
+ }
+
+ if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) &&
+ (flags & PVCLOCK_TSC_STABLE_BIT))
+ return ret;
+
+ /*
+ * Assumption here is that last_value, a global accumulator, always goes
+ * forward. If we are less than that, we should not be much smaller.
+ * We assume there is an error marging we're inside, and then the correction
+ * does not sacrifice accuracy.
+ *
+ * For reads: global may have changed between test and return,
+ * but this means someone else updated poked the clock at a later time.
+ * We just need to make sure we are not seeing a backwards event.
+ *
+ * For updates: last_value = ret is not enough, since two vcpus could be
+ * updating at the same time, and one of them could be slightly behind,
+ * making the assumption that last_value always go forward fail to hold.
+ */
+ last = atomic64_read(&last_value);
+ do {
+ if (ret < last)
+ return last;
+ last = atomic64_cmpxchg(&last_value, last, ret);
+ } while (unlikely(last != ret));
+
+ return ret;
+}
+
+void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock,
+ struct pvclock_vcpu_time_info *vcpu_time,
+ struct timespec64 *ts)
+{
+ u32 version;
+ u64 delta;
+ struct timespec64 now;
+
+ /* get wallclock at system boot */
+ do {
+ version = wall_clock->version;
+ rmb(); /* fetch version before time */
+ /*
+ * Note: wall_clock->sec is a u32 value, so it can
+ * only store dates between 1970 and 2106. To allow
+ * times beyond that, we need to create a new hypercall
+ * interface with an extended pvclock_wall_clock structure
+ * like ARM has.
+ */
+ now.tv_sec = wall_clock->sec;
+ now.tv_nsec = wall_clock->nsec;
+ rmb(); /* fetch time before checking version */
+ } while ((wall_clock->version & 1) || (version != wall_clock->version));
+
+ delta = pvclock_clocksource_read(vcpu_time); /* time since system boot */
+ delta += now.tv_sec * NSEC_PER_SEC + now.tv_nsec;
+
+ now.tv_nsec = do_div(delta, NSEC_PER_SEC);
+ now.tv_sec = delta;
+
+ set_normalized_timespec64(ts, now.tv_sec, now.tv_nsec);
+}
+
+void pvclock_set_pvti_cpu0_va(struct pvclock_vsyscall_time_info *pvti)
+{
+ WARN_ON(vclock_was_used(VCLOCK_PVCLOCK));
+ pvti_cpu0_va = pvti;
+}
+
+struct pvclock_vsyscall_time_info *pvclock_get_pvti_cpu0_va(void)
+{
+ return pvti_cpu0_va;
+}
+EXPORT_SYMBOL_GPL(pvclock_get_pvti_cpu0_va);