On Monday, 06.07.2015 at 16:41, Antti Kantee wrote: > On 06/07/15 14:43, Martin Lucina wrote: > >I have also put in a check that warns if the "TSC invariant" bit is not set > >in CPUID, however it turns out that neither KVM nor QEMU set this on my > >system, possibly on purpose. So halting if that flag is not set would not > >be very useful :-/ > > Doesn't QEMU set the flags based on which cpu you tell it to > emulate? Or are you saying the flag is stripped even if the host cpu > sets it and -cpu host is used?
The latter. It seems there's some work happened recently-ish regarding this. Under "KVM" in http://wiki.qemu.org/ChangeLog/2.1: New "invtsc" (Invariant TSC) CPU feature. When enabled, this will block migration and savevm, so it is not enabled by default on any CPU model. To enable invtsc, the migratable=no flag (supported only by -cpu host, by now) is required. So, invtsc is available only if using: -cpu host,migratable=no,+invtsc. I did try "-cpu host,migratable=no,+invtsc" on my machine but it doesn't make the warning go away...
