On Thu, Mar 24, 2022 at 06:13:03PM +0100, Paolo Bonzini wrote: > On 3/24/22 12:24, Paolo Bonzini wrote: > > That said, the VMware kbase does paint a slightly different picture. It > > implies that starting with hardware version 11 rebooting Windows is done > > through a hard reset instead of INIT. I'm not sure how that would be > > done, but in the meanwhile our fix should take care of do_cpu_init as > > well. > > Ok, so here are my findings: > > - Windows resets the system by writing 0xFE to port 0x64. This is a hard > reset on QEMU, but presumably it was a soft reset (INIT) on VMware until > version 10. > > - QEMU _does_ try to write 0 to the TSC on hard reset. But KVM special > cases 0 as "somebody is trying to hot-plug a new CPU" and wants to help out, > so it keeps the CPU synchronized with the previous TSC. > > So this is a pretty clear-cut QEMU bug. It can be fixed by e.g. writing 1 > to the TSC instead of 0.
Ah, excellant findings, so we won't need a config knob after all. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
