On Thu, 2020-06-25 at 21:17 +0200, Paolo Bonzini wrote: > On 25/06/20 20:56, Kevin Locke wrote: >>> Windows 10 can use the Hyper-V synthetic timer instead of the RTC, which >>> shouldn't have the problem. >> >> That's great news! Since I'm able to reproduce the issue on a >> recently installed Windows 10 2004 VM on Linux 5.7 with QEMU 5.0, is >> there anything I can do to help isolate the bug, or is it a known >> issue? > > You need to enable Hyper-V enlightenments, with something like > > -cpu host,hv_vpindex,hv_runtime,hv_synic,hv_stimer,hv_reset,hv_time,hv_relaxed > > on the QEMU command line. Bingo! I was using the defaults from virt-manager:[1] -cpu $host,hv-time,hv-relaxed,hv-vapic,hv-spinlocks=0x1fff Using to the enlightenments you suggested solves the high CPU when paused issue for me. After a bit of testing, it appears that hv_stimer is the key. High CPU when paused does not occur when that enlightenment is enabled, regardless of which others are enabled/disabled. Is there any reason not to add it to the virt-manager defaults for Windows 10? Any other suggestions about which enlightenments to enable or disable by default? Thanks again, Kevin [1]: https://github.com/virt-manager/virt-manager/blob/v2.2.1/virtinst/domain/features.py#L74-L83
