* Zhuangyanying (ann.zhuangyany...@huawei.com) wrote: > Hi all, > > Recently, I found migration failed when enable vPMU. > > migrate vPMU state was introduced in linux-3.10 + qemu-1.7. > > As long as enable vPMU, qemu will save / load the > vmstate_msr_architectural_pmu(msr_global_ctrl) register during the migration. > But global_ctrl generated based on cpuid(0xA), the number of general-purpose > performance > monitoring counters(PMC) can vary according to Intel SDN. The number of PMC > presented > to vm, does not support configuration currently, it depend on host cpuid, and > enable all pmc > defaultly at KVM. It cause migration to fail between boards with different > PMC counts. > > The return value of cpuid (0xA) is different dur to cpu, according to Intel > SDN，18-10 Vol. 3B: > > Note: The number of general-purpose performance monitoring counters (i.e. N > in Figure 18-9) > can vary across processor generations within a processor family, across > processor families, or > could be different depending on the configuration chosen at boot time in the > BIOS regarding > Intel Hyper Threading Technology, (e.g. N=2 for 45 nm Intel Atom processors; > N =4 for processors > based on the Nehalem microarchitecture; for processors based on the Sandy > Bridge > microarchitecture, N = 4 if Intel Hyper Threading Technology is active and > N=8 if not active). > > Also I found, N=8 if HT is not active based on the broadwell，, > such as CPU E7-8890 v4 @ 2.20GHz > > # ./x86_64-softmmu/qemu-system-x86_64 --enable-kvm -smp 4 -m 4096 -hda > /data/zyy/test_qemu.img.sles12sp1 -vnc :99 -cpu kvm64,pmu=true -incoming > tcp::8888 > Completed 100 % > qemu-system-x86_64: error: failed to set MSR 0x38f to 0x7000000ff > qemu-system-x86_64: /data/zyy/git/test/qemu/target/i386/kvm.c:1833: > kvm_put_msrs: > Assertion `ret == cpu->kvm_msr_buf->nmsrs' failed. > Aborted > > So make number of pmc configurable to vm ? Any better idea ?
Coincidentally we hit a similar problem a few days ago with -cpu host - it took me quite a while to spot the difference between the machines was the source had hyperthreading disabled. An option to set the number of counters makes sense to me; but I wonder how many other options we need as well. Also, I'm not sure there's any easy way for libvirt etc to figure out how many counters a host supports - it's not in /proc/cpuinfo. Dave > > Regards, > -Zhuang Yanying -- Dr. David Alan Gilbert / dgilb...@redhat.com / Manchester, UK
