El vie., 30 oct. 2020 a las 23:56, Bronek Kozicki (<b...@incorrekt.com>) escribió: > > I recently tried upgrading from vanilla LTS kernel 5.4 to vanilla 5.8 and > found that my virtual machines "stutter" when they did not previously. The > hypervisor is configured with tickless kernel (NO_HZ_FULL) and physical cores > are exclusively reserved for vcpus by means of isolcpus , nohz_full and > rcu_nocbs. The user experience under kernel 5.4 is good, it's only 5.8 when > stuttering happens. This could be either just a brief "pop" when playing > music, every few seconds, or actual short screen-freeze when playing games > under Windows VM (I use GPU pass-through with Nvidia Quadro cards). > > This seem to correspond with messages appearing on hypervisor console which > look like: > > [41426.188902] kvm [176116]: vcpu10, guest rIP: 0x7ff87a6a2aba ignored rdmsr: > 0x122 > [41426.202067] kvm [176116]: vcpu10, guest rIP: 0x7ff87a6a2aba ignored rdmsr: > 0x122 > [41426.218588] kvm [176116]: vcpu10, guest rIP: 0x7ff87b6d1d3a ignored rdmsr: > 0x122 > [41451.754213] kvm [1644425]: vcpu3, guest rIP: 0x7f5d4b442335 ignored rdmsr: > 0x122 > [41482.036754] kvm [176116]: vcpu2, guest rIP: 0x76f320ea ignored rdmsr: 0x122 > [41482.181285] kvm [176116]: vcpu2, guest rIP: 0x76f320ea ignored rdmsr: 0x122 > [41482.188947] kvm [176116]: vcpu2, guest rIP: 0x76d27f55 ignored rdmsr: 0x122 > > There is quite a lot of it, but only logged by kernel 5.8 and not by 5.4 (I > skipped 5.5 , 5.6 and 5.7). > > I build my own kernel roughly based on ArchLinux, but taking unaltered > sources directly from kernel.org and my own configuration tweaks (such as > CPU_FREQ_DEFAULT_GOV_PERFORMANCE=y , MCORE2=y , PREEMPT_VOLUNTARY=y , > NO_HZ_FULL=y , HZ_100=y , disable RCU_FAST_NO_HZ , disable X86_IOPL_IOPERM , > disable USERFAULTFD , disable XEN, disable PAGE_POISONING , disable > RAID6_PQ_BENCHMARK) > > The hypervisor box has 2x Xeon 2697v2 (12 cores per CPU, two sockets, 48 > physical threads) so there is plenty of CPU power left for I/O etc, despite > 12 cores (24 threads) reserved for vcpus only: nohz_full=6-17,30-41 > rcu_nocbs=6-17,30-41 isolcpus=6-17,30-41 . There are two VMs using these > reserved cores: > > <vcpu placement='static'>12</vcpu> > <iothreads>4</iothreads> > <cputune> > <vcpupin vcpu='0' cpuset='6'/> > <vcpupin vcpu='1' cpuset='30'/> > <vcpupin vcpu='2' cpuset='7'/> > <vcpupin vcpu='3' cpuset='31'/> > <vcpupin vcpu='4' cpuset='8'/> > <vcpupin vcpu='5' cpuset='32'/> > <vcpupin vcpu='6' cpuset='9'/> > <vcpupin vcpu='7' cpuset='33'/> > <vcpupin vcpu='8' cpuset='10'/> > <vcpupin vcpu='9' cpuset='34'/> > <vcpupin vcpu='10' cpuset='11'/> > <vcpupin vcpu='11' cpuset='35'/> > <emulatorpin cpuset='4-5,28-29'/> > <iothreadpin iothread='1' cpuset='0,24'/> > <iothreadpin iothread='2' cpuset='1,25'/> > <iothreadpin iothread='3' cpuset='2,26'/> > <iothreadpin iothread='4' cpuset='3,27'/> > </cputune> > <numatune> > <memory mode='strict' nodeset='0'/> > </numatune> > > ... and: > > <vcpu placement='static'>12</vcpu> > <iothreads>4</iothreads> > <cputune> > <vcpupin vcpu='0' cpuset='12'/> > <vcpupin vcpu='1' cpuset='36'/> > <vcpupin vcpu='2' cpuset='13'/> > <vcpupin vcpu='3' cpuset='37'/> > <vcpupin vcpu='4' cpuset='14'/> > <vcpupin vcpu='5' cpuset='38'/> > <vcpupin vcpu='6' cpuset='15'/> > <vcpupin vcpu='7' cpuset='39'/> > <vcpupin vcpu='8' cpuset='16'/> > <vcpupin vcpu='9' cpuset='40'/> > <vcpupin vcpu='10' cpuset='17'/> > <vcpupin vcpu='11' cpuset='41'/> > <emulatorpin cpuset='18-19,42-43'/> > <iothreadpin iothread='1' cpuset='20,44'/> > <iothreadpin iothread='2' cpuset='21,45'/> > <iothreadpin iothread='3' cpuset='22,46'/> > <iothreadpin iothread='4' cpuset='23,47'/> > </cputune> > <numatune> > <memory mode='strict' nodeset='1'/> > </numatune > > > There is no swap at all, the box has almost 400GB RAM. > > > B. > > -- > Bronek Kozicki > b...@incorrekt.com > > _______________________________________________ > vfio-users mailing list > vfio-users@redhat.com > https://www.redhat.com/mailman/listinfo/vfio-users >
try with └───╼ cat /etc/modprobe.d/kvm.conf options kvm ignore_msrs=0 greetings _______________________________________________ vfio-users mailing list vfio-users@redhat.com https://www.redhat.com/mailman/listinfo/vfio-users
