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. > > > 2) The solution to inject NMIs to the guest seemed overly > > complicated. > > Why do you need NMIs? > > All you need is a way to communicate to the guest that it should prepare > for clock madness to happen. Whether that's an IPI or a bit in a > hyperpage which gets checked during the update of the guest timekeeping > does not matter at all. > > But you certainly do not need an NMI because there is nothing useful you > can do within an NMI. > > Thanks, > > tglx
