Since commit a545ab6a ("kvm: x86: add tsc_offset field to struct
kvm_vcpu_arch", 2016-09-07) the offset between host and L1 TSC is
cached and need not be fished out of the VMCS or VMCB.  This means
that we can implement adjust_tsc_offset_guest and read_l1_tsc
entirely in generic code.  The simplification is particularly
significant for VMX code, where vmx->nested.vmcs01_tsc_offset
was duplicating what is now in vcpu->arch.tsc_offset.  Therefore
the vmcs01_tsc_offset can be dropped completely.

More importantly, this fixes KVM_GET_CLOCK/KVM_SET_CLOCK
which, after commit 108b249c ("KVM: x86: introduce get_kvmclock_ns",
2016-09-01) called read_l1_tsc while the VMCS was not loaded.
It thus returned bogus values on Intel CPUs.

Fixes: 108b249cReported-by: NRoman Kagan <rkagan@virtuozzo.com>
Reviewed-by: NRadim Krčmář <rkrcmar@redhat.com>
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>