On Mon, 2026-06-08 at 15:47 +0100, David Woodhouse wrote: > This is v5 of the series to clean up the KVM clock, rebased onto > tip/timers/ptp (which now includes Thomas's ktime snapshot series and > the read_snapshot patches for hyperv, kvmclock, and vmclock). > > The KVM clock has historically suffered from three problems: > > 1. Imprecision: get_kvmclock_ns() computed the clock from the *host* > TSC without applying guest TSC scaling, causing systemic drift from > the values the guest computes from its own TSC. > > 2. Unnecessary discontinuities: gratuitous KVM_REQ_MASTERCLOCK_UPDATE > requests caused the master clock reference point to be re-snapshotted, > yanking the guest's clock due to arithmetic precision differences. > > 3. No precise migration API: the existing KVM_[GS]ET_CLOCK only allows > setting the clock at a given UTC reference time, which is necessarily > imprecise. There was no way to preserve the exact arithmetic > relationship between guest TSC and KVM clock across live migration. > > This series addresses all three, and adds new APIs for precise clock > migration and TSC frequency reporting. As an added bonus, it now rips > out the whole pvclock_gtod_data hack which was shadowing the kernel's > timekeeping, and uses ktime snapshots as $DEITY (well, Thomas) intended.
Updated series with Sashiko's fixes pushed out to https://git.infradead.org/?p=users/dwmw2/linux.git;a=shortlog;h=refs/heads/kvmclock6 I'll give it a while for meat-based reviewers to opine before sending another round. (Is there a way to get Sashiko to take another look without sending it all to the list again?)
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