On 10/08/2015 16:14, Jintack Lim wrote: >> > Yes, you just use the TSC. :) However, you first have to check that the >> > TSC is consistent across CPUs. On older machines it's not, but the >> > kernel can detect it. > Thanks, Paolo. > > What would be the best way to check if TSC is consistent across CPUs? You need to have boot_cpu_has(X86_FEATURE_CONSTANT_TSC) and boot_cpu_has(X86_FEATURE_NONSTOP_TSC). However, I would just use TAI (ktime_get_clocktai). x86 KVM provides a paravirtual interface that synchronizes CLOCK_TAI with the host, and using it is the simplest way to get synchronized times between the host and the guest. Paolo > Is it synchronized in nano second (or even cpu clock cycle) resolution? > > To get synchronized tsc across the host and the guest, > just calling rdtscll() in host and guest would be enough? -- 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
