2016-01-19 13:18+0530, Dixon Xavier: > We need to use the time stamp counter in guest, were looking if the > constant_tsc & nonstop_tsc functionalities can be enabled in qemu-kvm > guest. > > we can't see constant_tsc & nonstop_tsc flags in the 'Recognized CPUID > flags' section. constant_tsc and nonstop_tsc aren't CPUID flags, they are Linux CPU flags that describe a quality of TSC. The CPUID flag you are looking for is "invtsc" (invariant TSC). Linux will report both constant_tsc and nonstop_tsc when invtsc is present. > # /usr/libexec/qemu-kvm --version > QEMU emulator version 1.5.3 (qemu-kvm-1.5.3-60.el7_0.11), Copyright invtsc is not available in that QEMU, upstream added it in v2.1.0. > Is it supported in qemu-kvm ? Yes, if your host CPU has invtsc and QEMU knows about it. (Btw. invtsc in QEMU doesn't change the quality of guest's TSC, but it's very unwise to depend on it.) > If yes, how can we get this work in guest ? You must disable migrations, -cpu host,migratable=off This thread has a somewhat relevant discussion: http://www.spinics.net/lists/kvm/msg125867.html -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
