Re: [PATCH 1/2] KVM: x86: implement KVM_SET_TSC_PRECISE/KVM_GET_TSC_PRECISE

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On 30/11/20 14:35, Maxim Levitsky wrote:
+		if (guest_cpuid_has(vcpu, X86_FEATURE_TSC_ADJUST)) {
+			tsc_state.tsc_adjust = vcpu->arch.ia32_tsc_adjust_msr;
+			tsc_state.flags |= KVM_TSC_STATE_TSC_ADJUST_VALID;
+		}

This is mostly useful for userspace that doesn't disable the quirk, right?

+		kvm_get_walltime(&wall_nsec, &host_tsc);
+		diff = wall_nsec - tsc_state.nsec;
+
+		if (diff < 0 || tsc_state.nsec == 0)
+			diff = 0;
+

diff < 0 should be okay. Also why the nsec==0 special case? What about using a flag instead?

Paolo




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