Re: [PATCH 07/10] KVM: x86: Avoid NTP frequency skew for KVM clock on 32-bit host

From: Paul Durrant
Date: Fri Apr 19 2024 - 11:54:00 EST


On 18/04/2024 20:34, David Woodhouse wrote:
From: David Woodhouse <dwmw@xxxxxxxxxxxx>

Commit 53fafdbb8b21 ("KVM: x86: switch KVMCLOCK base to monotonic raw
clock") did so only for 64-bit hosts, by capturing the boot offset from
within the existing clocksource notifier update_pvclock_gtod().

That notifier was added in commit 16e8d74d2da9 ("KVM: x86: notifier for
clocksource changes") but only on x86_64, because its original purpose
was just to disable the "master clock" mode which is only supported on
x86_64.

Now that the notifier is used for more than disabling master clock mode,
(well, OK, more than a decade later but clocks are hard), enable it for
the 32-bit build too so that get_kvmclock_base_ns() can be unaffected by
NTP sync on 32-bit too.

Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx>
---
arch/x86/kvm/x86.c | 18 ++++++------------
1 file changed, 6 insertions(+), 12 deletions(-)


Reviewed-by: Paul Durrant <paul@xxxxxxx>