[RFC PATCH 7/8] KVM: x86: Remove pvclock_gtod_data and private timekeeping code
From: David Woodhouse
Date: Tue May 26 2026 - 19:07:59 EST
From: David Woodhouse <dwmw@xxxxxxxxxxxx>
Remove the now-unused KVM-private timekeeping infrastructure:
- struct pvclock_clock and struct pvclock_gtod_data
- update_pvclock_gtod() and its seqcount-protected state copy
- read_tsc() (KVM's private TSC reader with cycle_last clamping)
- vgettsc() (KVM's private clocksource interpolation)
- do_kvmclock_base(), do_monotonic(), do_realtime()
Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
Assisted-by: Kiro:claude-opus-4.6-1m
---
arch/x86/kvm/x86.c | 175 ---------------------------------------------
1 file changed, 175 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index c31b19860c13..2c34b973fce0 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -2347,58 +2347,6 @@ static int do_set_msr(struct kvm_vcpu *vcpu, unsigned index, u64 *data)
return kvm_set_msr_ignored_check(vcpu, index, *data, true);
}
-struct pvclock_clock {
- int vclock_mode;
- u64 cycle_last;
- u64 mask;
- u32 mult;
- u32 shift;
- u64 base_cycles;
- u64 offset;
-};
-
-struct pvclock_gtod_data {
- seqcount_t seq;
-
- struct pvclock_clock clock; /* extract of a clocksource struct */
- struct pvclock_clock raw_clock; /* extract of a clocksource struct */
-
- ktime_t offs_boot;
- u64 wall_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->tkr_mono.clock->vdso_clock_mode;
- vdata->clock.cycle_last = tk->tkr_mono.cycle_last;
- vdata->clock.mask = tk->tkr_mono.mask;
- vdata->clock.mult = tk->tkr_mono.mult;
- vdata->clock.shift = tk->tkr_mono.shift;
- vdata->clock.base_cycles = tk->tkr_mono.xtime_nsec;
- vdata->clock.offset = tk->tkr_mono.base;
-
- vdata->raw_clock.vclock_mode = tk->tkr_raw.clock->vdso_clock_mode;
- vdata->raw_clock.cycle_last = tk->tkr_raw.cycle_last;
- vdata->raw_clock.mask = tk->tkr_raw.mask;
- vdata->raw_clock.mult = tk->tkr_raw.mult;
- vdata->raw_clock.shift = tk->tkr_raw.shift;
- vdata->raw_clock.base_cycles = tk->tkr_raw.xtime_nsec;
- vdata->raw_clock.offset = tk->tkr_raw.base;
-
- vdata->wall_time_sec = tk->xtime_sec;
-
- vdata->offs_boot = tk->offs_boot;
-
- write_seqcount_end(&vdata->seq);
-}
-
static s64 get_kvmclock_base_ns(void)
{
/* Count up from boot time, but with the frequency of the raw clock. */
@@ -3012,128 +2960,6 @@ static inline void adjust_tsc_offset_host(struct kvm_vcpu *vcpu, s64 adjustment)
#ifdef CONFIG_X86_64
-static u64 read_tsc(void)
-{
- u64 ret = (u64)rdtsc_ordered();
- u64 last = pvclock_gtod_data.clock.cycle_last;
-
- if (likely(ret >= last))
- return ret;
-
- /*
- * GCC likes to generate cmov here, but this branch is extremely
- * predictable (it's just a function of time and the likely is
- * very likely) and there's a data dependence, so force GCC
- * to generate a branch instead. I don't barrier() because
- * we don't actually need a barrier, and if this function
- * ever gets inlined it will generate worse code.
- */
- asm volatile ("");
- return last;
-}
-
-static inline u64 vgettsc(struct pvclock_clock *clock, u64 *tsc_timestamp,
- int *mode)
-{
- u64 tsc_pg_val;
- long v;
-
- switch (clock->vclock_mode) {
- case VDSO_CLOCKMODE_HVCLOCK:
- if (hv_read_tsc_page_tsc(hv_get_tsc_page(),
- tsc_timestamp, &tsc_pg_val)) {
- /* TSC page valid */
- *mode = VDSO_CLOCKMODE_HVCLOCK;
- v = (tsc_pg_val - clock->cycle_last) &
- clock->mask;
- } else {
- /* TSC page invalid */
- *mode = VDSO_CLOCKMODE_NONE;
- }
- break;
- case VDSO_CLOCKMODE_TSC:
- *mode = VDSO_CLOCKMODE_TSC;
- *tsc_timestamp = read_tsc();
- v = (*tsc_timestamp - clock->cycle_last) &
- clock->mask;
- break;
- default:
- *mode = VDSO_CLOCKMODE_NONE;
- }
-
- if (*mode == VDSO_CLOCKMODE_NONE)
- *tsc_timestamp = v = 0;
-
- return v * clock->mult;
-}
-
-/*
- * As with get_kvmclock_base_ns(), this counts from boot time, at the
- * frequency of CLOCK_MONOTONIC_RAW (hence adding gtos->offs_boot).
- */
-static int do_kvmclock_base(s64 *t, u64 *tsc_timestamp)
-{
- struct pvclock_gtod_data *gtod = &pvclock_gtod_data;
- unsigned long seq;
- int mode;
- u64 ns;
-
- do {
- seq = read_seqcount_begin(>od->seq);
- ns = gtod->raw_clock.base_cycles;
- ns += vgettsc(>od->raw_clock, tsc_timestamp, &mode);
- ns >>= gtod->raw_clock.shift;
- ns += ktime_to_ns(ktime_add(gtod->raw_clock.offset, gtod->offs_boot));
- } while (unlikely(read_seqcount_retry(>od->seq, seq)));
- *t = ns;
-
- return mode;
-}
-
-/*
- * This calculates CLOCK_MONOTONIC at the time of the TSC snapshot, with
- * no boot time offset.
- */
-static int do_monotonic(s64 *t, u64 *tsc_timestamp)
-{
- struct pvclock_gtod_data *gtod = &pvclock_gtod_data;
- unsigned long seq;
- int mode;
- u64 ns;
-
- do {
- seq = read_seqcount_begin(>od->seq);
- ns = gtod->clock.base_cycles;
- ns += vgettsc(>od->clock, tsc_timestamp, &mode);
- ns >>= gtod->clock.shift;
- ns += ktime_to_ns(gtod->clock.offset);
- } while (unlikely(read_seqcount_retry(>od->seq, seq)));
- *t = ns;
-
- return mode;
-}
-
-static int do_realtime(struct timespec64 *ts, u64 *tsc_timestamp)
-{
- struct pvclock_gtod_data *gtod = &pvclock_gtod_data;
- unsigned long seq;
- int mode;
- u64 ns;
-
- do {
- seq = read_seqcount_begin(>od->seq);
- ts->tv_sec = gtod->wall_time_sec;
- ns = gtod->clock.base_cycles;
- ns += vgettsc(>od->clock, tsc_timestamp, &mode);
- ns >>= gtod->clock.shift;
- } while (unlikely(read_seqcount_retry(>od->seq, seq)));
-
- ts->tv_sec += __iter_div_u64_rem(ns, NSEC_PER_SEC, &ns);
- ts->tv_nsec = ns;
-
- return mode;
-}
-
/*
* Calculates the kvmclock_base_ns (CLOCK_MONOTONIC_RAW + boot time) and
* reports the TSC value from which it do so. Returns true if host is
@@ -10362,7 +10188,6 @@ static int pvclock_gtod_notify(struct notifier_block *nb, unsigned long unused,
{
struct timekeeper *tk = priv;
- update_pvclock_gtod(tk);
#ifdef CONFIG_X86_64
kvm_host_has_tsc_clocksource =
--
2.54.0