From: Sean Christopherson <seanjc@google.com>
To: Krish Sadhukhan <krish.sadhukhan@oracle.com>
Cc: kvm@vger.kernel.org, pbonzini@redhat.com, jmattson@google.com
Subject: Re: [PATCH 1/3] KVM: nVMX: Move 'nested_run' counter to enter_guest_mode()
Date: Wed, 12 May 2021 18:30:00 +0000 [thread overview]
Message-ID: <YJweqOAxMITSmKs2@google.com> (raw)
In-Reply-To: <20210512014759.55556-2-krish.sadhukhan@oracle.com>
On Tue, May 11, 2021, Krish Sadhukhan wrote:
> Move 'nested_run' counter to enter_guest_mode() because,
> i) This counter is common to both Intel and AMD and can be incremented
> from a common place,
> ii) guest mode is a more finer-grained state than the beginning of
> nested_svm_vmrun() and nested_vmx_run().
Hooking enter_guest_mode() makes the name a misnomer since it will count cases
such as setting nested state and resuming from SMI, neither of which is a nested
run in the sense of L1 deliberately choosing to run L2.
And while bumping nested_run at the very beginning of VMLAUNCH/VMRESUME/VMRUN is
arguably wrong in that it counts _attempts_ instead of successful VM-Enters, it's
at least consistent. Moving this to enter_guest_mode() means it's arbitrarily
counting VM-Enter that fails late, but not those that fail early.
If we really want it to mean "successful VM-Enter", then we should wait until
after VM-Enter actual succeeds, and do it only for actual VM-Enter.
next prev parent reply other threads:[~2021-05-12 19:45 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-12 1:47 [PATCH 0/3] KVM: nVMX: Add more statistics to KVM debugfs Krish Sadhukhan
2021-05-12 1:47 ` [PATCH 1/3] KVM: nVMX: Move 'nested_run' counter to enter_guest_mode() Krish Sadhukhan
2021-05-12 18:30 ` Sean Christopherson [this message]
2021-05-13 16:02 ` Dongli Zhang
2021-05-12 1:47 ` [PATCH 2/3] KVM: nVMX: Add a new VCPU statistic to show if VCPU is running nested guest Krish Sadhukhan
2021-05-12 16:01 ` Jim Mattson
2021-05-12 17:56 ` Krish Sadhukhan
2021-05-12 17:59 ` Jim Mattson
2021-05-12 18:19 ` Sean Christopherson
2021-05-12 1:47 ` [PATCH 3/3] KVM: x86: Add a new VM statistic to show number of VCPUs created in a given VM Krish Sadhukhan
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