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Re: timekeeping regression?



At Sat, 08 Jun 2024 05:01:00 +0000, "Mathew, Cherry G." <c%bow.st@localhost> wrote:
Subject: Re: timekeeping regression?
>
> Is it possible that you have a handy matrix of versions of NetBSD/Xen
> that work/don't work perhaps ?

Not exactly....

I think all recent releases of NetBSD are affected, including -current
back to 2021-03 or so; at least those using a XEN3_DOMU kernel in a
type="pv" container (I haven't tested very bleeding edge -current, but
plan to as soon as I can get to it, nor have I tested any 8.x, and my
memory is a bit fuzzy about official 9.x).

For me these problems first showed up for me with Xen-4.18, but I'm
fairly certain they also affect Xen-4.15 (I just didn't run it).

There were no problems with Xen-4.11 (or any before, e.g. 4.5, 4.8), and
I think Xen-4.13 was also OK, but my memory has more fuzzies and I can't
find any really useful record of package installations (the pkgin
"pkg_install-err.log" file would suffice, but it doesn't include the
year!!!).

I had FreeBSD-12 running somewhere once (under full hvm), but I think
I've only had FreeBSD-14 running with Xen-4.18 (under pvh).  In any case
FreeBSD has never had timekeeping problems for me under Xen.

There's one more thing that I may already have mentioned, but which
continues to confuse me.  Both domUs and the dom0 use "xen_system_time"
as their timecounter, so timekeeping should behave exactly the same for
dom0 as well, but so far I don't have any trouble with dom0s keeping
good time, and the in fact the dom0's run on-time even when all their
hosted domUs are wandering irretrievably.

As a side note:  NetBSD can't keep time under VirtualBox (on macos), at
least not the way I was trying to run it.  However it works A-OK under
the macos hypervisor (x86 that is, I'm using UTM to configure and manage
it, and UTM uses QEMU for device emulation).  It's using ichlpcib0 as
its preferred timecounter (with TSC having been given a q of -100).

--
					Greg A. Woods <gwoods%acm.org@localhost>

Kelowna, BC     +1 250 762-7675           RoboHack <woods%robohack.ca@localhost>
Planix, Inc. <woods%planix.com@localhost>     Avoncote Farms <woods%avoncote.ca@localhost>

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