Hello, I've faced the issue with qemu [1]. And It looks like qemu developers seem not going to do something with it. In brief, the issue here that qemu rely on kvm's get cpuid ioctl behavior. When qemu want to know perfcounter presence it asks 0xa register through the ioctl and check if version is non-zero. However, Intel docs clearly state that it is not enough (see 4.3. of [2]). Additionally IA32_MISC_ENABLE has to be checked to ensure that perfcounters aren't just possible in hardware but also actually enabled. qemu makes no difference between this two cases. So, would it be possible to introduce another quirk in __do_cpuid_ent (checking IA32_MISC_ENABLE and putting zero to 0xa version) to make qemu devs happy? [1] https://bugs.launchpad.net/qemu/+bug/1661386 [2] https://software.intel.com/sites/default/files/m/5/2/c/f/1/30320-Nehalem-PMU-Programming-Guide-Core.pdf -- With best regards, Matwey V. Kornilov
