On 12/04/2018 19:21, Raslan, KarimAllah wrote:
> Now looking further at the code, it seems that everywhere in the code
> tsc_offset is treated as the L01 TSC_OFFSET.
>
> Like here:
>
> if (vmcs12->cpu_based_vm_exec_control &
> CPU_BASED_USE_TSC_OFFSETING)
> vmcs_write64(TSC_OFFSET,
> vcpu->arch.tsc_offset + vmcs12->tsc_offset);
>
> and here:
>
> vmcs_write64(TSC_OFFSET, vcpu->arch.tsc_offset);
>
> and here:
>
> u64 kvm_read_l1_tsc(struct kvm_vcpu *vcpu, u64 host_tsc)
> {
> return vcpu->arch.tsc_offset + kvm_scale_tsc(vcpu, host_tsc);
> }
> EXPORT_SYMBOL_GPL(kvm_read_l1_tsc);
>
> ... would not it be simpler and more inline with the current code to
> just do what I did above + remove the "+ l1_tsc_offset" + probably
> document tsc_offset ?
Problem is, I don't think it's correct. :) A good start would be to try
disabling MSR_IA32_TSC interception in KVM, prepare a kvm-unit-tests
test that reads the MSR, and see if you get the host or guest TSC...
Paolo
