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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.

  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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