On 5/20/21 9:57 AM, Jim Mattson wrote:
On Thu, May 20, 2021 at 7:56 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:
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?
It was in the context of a proposed stat to indicate how many vCPUs
are *currently* running nested guests that I said I'd rather just know
how many vCPUs had *ever* run nested guests. I don't need a separate
stat. Checking vcpu->stat.nested_run for non-zero values works fine
for me.
I will fall back to my v1 idea then. That's at least useful if we want
to create a time graph of VCPUs running nested guests.
