Re: [PATCH 1/2] KVM: x86: reorganize pvclock_gtod_data members

Paolo Bonzini pbonzini@redhat.com writes:

We will need a copy of tk->offs_boot in the next patch. Store it and cleanup the struct: instead of storing tk->tkr_xxx.base with the tk->offs_boot included, store the raw value in struct pvclock_clock and sum tk->offs_boot in do_monotonic_raw and do_realtime. tk->tkr_xxx.xtime_nsec also moves to struct pvclock_clock.

While at it, fix a (usually harmless) typo in do_monotonic_raw, which was using gtod->clock.shift instead of gtod->raw_clock.shift.

Fixes: 53fafdbb8b21f ("KVM: x86: switch KVMCLOCK base to monotonic raw clock") Cc: stable@vger.kernel.org Signed-off-by: Paolo Bonzini pbonzini@redhat.com

---

arch/x86/kvm/x86.c | 29 ++++++++++++----------------- 1 file changed, 12 insertions(+), 17 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 89621025577a..1b4273cce63c 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1532,6 +1532,8 @@ struct pvclock_clock { u64 mask; u32 mult; u32 shift;

• u64 base_cycles;
• u64 offset;

}; struct pvclock_gtod_data { @@ -1540,11 +1542,8 @@ struct pvclock_gtod_data { struct pvclock_clock clock; /* extract of a clocksource struct */ struct pvclock_clock raw_clock; /* extract of a clocksource struct */

• u64 boot_ns_raw;
• u64 boot_ns;
• u64 nsec_base;

• ktime_t offs_boot; u64 wall_time_sec;

• u64 monotonic_raw_nsec;

}; static struct pvclock_gtod_data pvclock_gtod_data; @@ -1552,10 +1551,6 @@ struct pvclock_gtod_data { static void update_pvclock_gtod(struct timekeeper *tk) { struct pvclock_gtod_data *vdata = &pvclock_gtod_data;

• u64 boot_ns, boot_ns_raw;
• boot_ns = ktime_to_ns(ktime_add(tk->tkr_mono.base, tk->offs_boot));
• boot_ns_raw = ktime_to_ns(ktime_add(tk->tkr_raw.base, tk->offs_boot));

write_seqcount_begin(&vdata->seq); @@ -1565,20 +1560,20 @@ static void update_pvclock_gtod(struct timekeeper *tk) 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->archdata.vclock_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->boot_ns = boot_ns;
• vdata->nsec_base = tk->tkr_mono.xtime_nsec;

• vdata->raw_clock.base_cycles = tk->tkr_raw.xtime_nsec;
• vdata->raw_clock.offset = tk->tkr_raw.base;

Likely a personal preference but the suggested naming is a bit confusing: we use 'base_cycles' to keep 'xtime_nsec' and 'offset' to keep ... 'base'. Not that I think that 'struct timekeeper' is perfect but at least it is documented. Should we maybe just stick to it (and name 'struct pvclock_clock' fields accordingly?)

vdata->wall_time_sec = tk->xtime_sec;

• vdata->boot_ns_raw = boot_ns_raw;
• vdata->monotonic_raw_nsec = tk->tkr_raw.xtime_nsec;

• vdata->offs_boot = tk->offs_boot;

write_seqcount_end(&vdata->seq); } @@ -2048,10 +2043,10 @@ static int do_monotonic_raw(s64 *t, u64 *tsc_timestamp) do { seq = read_seqcount_begin(&gtod->seq);

• ns = gtod->monotonic_raw_nsec;
  

• ns = gtod->raw_clock.base_cycles;
  

  ns += vgettsc(&gtod->raw_clock, tsc_timestamp, &mode);

• ns >>= gtod->clock.shift;
  

• ns += gtod->boot_ns_raw;
  

• ns >>= gtod->raw_clock.shift;
  

• ns += ktime_to_ns(ktime_add(gtod->raw_clock.offset, gtod->offs_boot));
  

  } while (unlikely(read_seqcount_retry(&gtod->seq, seq))); *t = ns;

@@ -2068,7 +2063,7 @@ static int do_realtime(struct timespec64 *ts, u64 *tsc_timestamp) do { seq = read_seqcount_begin(&gtod->seq); ts->tv_sec = gtod->wall_time_sec;

• ns = gtod->nsec_base;
  

• ns = gtod->clock.base_cycles;
  

  ns += vgettsc(&gtod->clock, tsc_timestamp, &mode); ns >>= gtod->clock.shift; } while (unlikely(read_seqcount_retry(&gtod->seq, seq)));

FWIW,

Reviewed-by: Vitaly Kuznetsov vkuznets@redhat.com