2017-04-13 15:05+0100, Stefan Hajnoczi: > On Wed, Apr 12, 2017 at 09:11:12PM +0200, Jean Baptiste Guerraz wrote: > > Hello, > > > > We're facing an issue with a Windows guest VM which runs quite well on > > a laptop (Fedora 25 - Core I7 4720HQ - > > https://www.asus.com/Notebooks/N551JX/specifications/ ) but not on 2 > > different servers (one Debian 8 on > > https://documentation.online.net/en/dedicated-server/offers/2015/server-dedibox-pro-2015-gen2#server_dedibox_pro_2015_gen2 > > - and one Fedora 25 on > > https://documentation.online.net/en/dedicated-server/offers/2016/server-dedibox-md-2016#server_dedibox_md_2016) Interesting, is there some consistent difference between grep . /sys/module/kvm*/parameters/* on those systems? > > qemu-system-x86 7420 [000] 28829.151599: kvm:kvm_mmio: mmio read len > > 4 gpa 0xfed000f0 val 0x5e3c5955 > > This is the physical address range of the HPET (timer). Right, disabling HPET is worth a shot. :) > > If one of you have an idea about how to dig further, that would be super :) > > I looked at a few of the interrupts that were injected. An interrupt is > interrupt delivered every 15 milliseconds. They were immediately > acknowledged by the interrupt handler function inside the guest. > > This just looks like a running guest that's doing no I/O to me. It had two vector 47 interrupts earlier and those only got delivered after TPR was lowered, so the problem could a bug in KVM's TPR handling, which only allows vector 209 after some point? > Can anyone else spot something suspicious that indicates 100% guest CPU > consumption? It seems to be reading HPET in a tight loop. No idea why, though. So far, I'd compare kvm parameters, disable HPET, and check TPR, to see where that goes, thanks.
