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    SubjectRe: [PATCH v3 10/12] KVM: VMX: Set the TSC offset and multiplier on nested entry and exit
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    On Fri, 2021-05-21 at 11:24 +0100, Ilias Stamatis wrote:
    > Calculate the nested TSC offset and multiplier on entering L2 using the
    > corresponding functions. Restore the L1 values on L2's exit.
    >
    > Signed-off-by: Ilias Stamatis <ilstam@amazon.com>
    > ---
    > arch/x86/kvm/vmx/nested.c | 18 ++++++++++++++----
    > 1 file changed, 14 insertions(+), 4 deletions(-)
    >
    > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
    > index 239154d3e4e7..f75c4174cbcf 100644
    > --- a/arch/x86/kvm/vmx/nested.c
    > +++ b/arch/x86/kvm/vmx/nested.c
    > @@ -2532,6 +2532,15 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
    > vmcs_write64(GUEST_IA32_PAT, vmx->vcpu.arch.pat);
    > }
    >
    > + vcpu->arch.tsc_offset = kvm_calc_nested_tsc_offset(
    > + vcpu->arch.l1_tsc_offset,
    > + vmx_get_l2_tsc_offset(vcpu),
    > + vmx_get_l2_tsc_multiplier(vcpu));
    > +
    > + vcpu->arch.tsc_scaling_ratio = kvm_calc_nested_tsc_multiplier(
    > + vcpu->arch.l1_tsc_scaling_ratio,
    > + vmx_get_l2_tsc_multiplier(vcpu));
    > +

    This code can be in theory put to the common x86 code,
    since it uses the vendor callbacks anyway, but this is
    probably not worth it.

    > vmcs_write64(TSC_OFFSET, vcpu->arch.tsc_offset);
    > if (kvm_has_tsc_control)
    > vmcs_write64(TSC_MULTIPLIER, vcpu->arch.tsc_scaling_ratio);
    > @@ -3353,8 +3362,6 @@ enum nvmx_vmentry_status nested_vmx_enter_non_root_mode(struct kvm_vcpu *vcpu,
    > }
    >
    > enter_guest_mode(vcpu);
    > - if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETTING)
    > - vcpu->arch.tsc_offset += vmcs12->tsc_offset;
    >
    > if (prepare_vmcs02(vcpu, vmcs12, &entry_failure_code)) {
    > exit_reason.basic = EXIT_REASON_INVALID_STATE;
    > @@ -4462,8 +4469,11 @@ void nested_vmx_vmexit(struct kvm_vcpu *vcpu, u32 vm_exit_reason,
    > if (nested_cpu_has_preemption_timer(vmcs12))
    > hrtimer_cancel(&to_vmx(vcpu)->nested.preemption_timer);
    >
    > - if (vmcs12->cpu_based_vm_exec_control & CPU_BASED_USE_TSC_OFFSETTING)
    > - vcpu->arch.tsc_offset -= vmcs12->tsc_offset;
    > + if (nested_cpu_has(vmcs12, CPU_BASED_USE_TSC_OFFSETTING)) {
    > + vcpu->arch.tsc_offset = vcpu->arch.l1_tsc_offset;
    > + if (nested_cpu_has2(vmcs12, SECONDARY_EXEC_TSC_SCALING))
    > + vcpu->arch.tsc_scaling_ratio = vcpu->arch.l1_tsc_scaling_ratio;
    > + }

    Same here.
    >
    > if (likely(!vmx->fail)) {
    > sync_vmcs02_to_vmcs12(vcpu, vmcs12);


    Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>

    Best regards,
    Maxim Levitsky

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