On Thu, Dec 10, 2020 at 10:48:10PM +0100, Thomas Gleixner wrote: > On Thu, Dec 10 2020 at 12:26, Marcelo Tosatti wrote: > > On Wed, Dec 09, 2020 at 09:58:23PM +0100, Thomas Gleixner wrote: > >> Marcelo, > >> > >> On Wed, Dec 09 2020 at 13:34, Marcelo Tosatti wrote: > >> > On Tue, Dec 08, 2020 at 10:33:15PM +0100, Thomas Gleixner wrote: > >> >> On Tue, Dec 08 2020 at 15:11, Marcelo Tosatti wrote: > >> >> > max_cycles overflow. Sent a message to Maxim describing it. > >> >> > >> >> Truly helpful. Why the hell did you not talk to me when you ran into > >> >> that the first time? > >> > > >> > Because > >> > > >> > 1) Users wanted CLOCK_BOOTTIME to stop counting while the VM > >> > is paused (so we wanted to stop guest clock when VM is paused anyway). > >> > >> How is that supposed to work w/o the guest kernels help if you have to > >> keep clock realtime up to date? > > > > Upon VM resume, we notify NTP daemon in the guest to sync realtime > > clock. > > Brilliant. What happens if there is no NTP daemon? What happens if the > NTP daemon is not part of the virt orchestration magic and cannot be > notified, then it will notice the time jump after the next update > interval. > > What about correctness? > > ALL CLOCK_* stop and resume when the VM is resumed at the point where > they stopped. > > So up to the point where NTP catches up and corrects clock realtime and > TAI other processes can observe that time jumped in the outside world, > e.g. via a network packet or whatever, but there is no reason why time > should have jumped outside vs. the local one. > > You really all live in a seperate universe creating your own rules how > things which other people work hard on to get it correct can be screwed > over. 1. T = read timestamp. 2. migrate (VM stops for a certain period). 3. use timestamp T. > Of course this all is nowhere documented in detail. At least a quick > search with about 10 different keyword combinations revealed absolutely > nothing. > > This features first, correctness later frenzy is insane and it better > stops now before you pile even more crap on the existing steaming pile > of insanities. Sure.
