On Wed, May 19, 2021, Krish Sadhukhan wrote:
> Add a new debugfs statistic to show how many VCPUs have run nested guests.
> This statistic considers only the first time a given VCPU successfully runs
> a nested guest.
>
> Signed-off-by: Krish Sadhukhan <Krish.Sadhukhan@xxxxxxxxxx>
> Suggested-by: Jim Mattson <jmattson@xxxxxxxxxx>
> ---
> arch/x86/include/asm/kvm_host.h | 1 +
> arch/x86/kvm/svm/svm.c | 5 ++++-
> arch/x86/kvm/vmx/vmx.c | 5 ++++-
> arch/x86/kvm/x86.c | 1 +
> 4 files changed, 10 insertions(+), 2 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index cf8557b2b90f..a19fe2cfaa93 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1138,6 +1138,7 @@ struct kvm_vm_stat {
> ulong lpages;
> ulong nx_lpage_splits;
> ulong max_mmu_page_hash_collisions;
> + ulong vcpus_ran_nested;
> };
>
> struct kvm_vcpu_stat {
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 57c351640355..d1871c51411f 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -3876,8 +3876,11 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu)
> /* Track VMRUNs that have made past consistency checking */
> if (svm->nested.nested_run_pending &&
> svm->vmcb->control.exit_code != SVM_EXIT_ERR &&
> - svm->vmcb->control.exit_code != SVM_EXIT_NPF)
> + svm->vmcb->control.exit_code != SVM_EXIT_NPF) {
> + if (!vcpu->stat.nested_runs)
> + ++vcpu->kvm->stat.vcpus_ran_nested;
Using a separate counter seems unnecessary, userspace can aggregate
vcpu->stat.nested_run itself to see how many vCPUs have done nested VM-Enter.
Jim, were you thinking of something else? Am I missing something?
