At Thu, 22 May 2025 08:31:04 -0400, Greg Troxel <gdt%lexort.com@localhost> wrote: Subject: Re: CVS commit: src/sys/arch/xen/xen > > "Taylor R Campbell" <riastradh%netbsd.org@localhost> writes: > > > Module Name: src > > Committed By: riastradh > > Date: Thu May 22 12:08:57 UTC 2025 > > > > Modified Files: > > src/sys/arch/xen/xen: xen_clock.c > > > > Log Message: > > xen: Use ordered rdtsc() function, rather than inline rdtsc asm. > > > > This will issue either lfence, mfence, or cpuid before the rdtsc > > instruction, depending on the CPU identification, in order to prevent > > reordering with respect to surrounding loads -- particularly those > > used to query the host's systime parameters. Ah ha. Very interesting! > > May help with: > > > > PR port-xen/59437: Xen time stability > > I am guessing that > > This change is intended for dom0 and domU, in all NetBSD versions. > > Pending testing, would be pulled up to 10 and 9. > > Testing means just pulling up this diff locally and booting a new > kernel. > > but if I am guessing wrong, a clue would be appreciataed. I'm testing this change, but in my refactored version of xen_clock. So far it looks a wee bit more stable, especially in a domU, but possibly also in the dom0. FYI I'm running it on approximately xen-4.20-rc1. We'll know in a week if it fixes anything. -- 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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