linux-kernel - Re: [PATCH] KVM: VMX: CPU frequency scaling for intel x86

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Message-ID: <0194b22a-38a1-08a1-a576-de6463389ce4@redhat.com>
Date:   Tue, 31 May 2022 20:11:33 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Metin Kaya <metikaya@...zon.co.uk>, jalliste@...zon.com
Cc:     bp@...en8.de, diapop@...zon.co.uk, hpa@...or.com,
        jmattson@...gle.com, joro@...tes.org, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, mingo@...hat.com, rkrcmar@...hat.com,
        sean.j.christopherson@...el.com, tglx@...utronix.de,
        vkuznets@...hat.com, wanpengli@...cent.com, x86@...nel.org
Subject: Re: [PATCH] KVM: VMX: CPU frequency scaling for intel x86_64 KVM
 guests

On 5/31/22 13:43, Metin Kaya wrote:
> Thanks, Jack.
> 
> Reviewed-by: Metin Kaya <metikaya@...zon.co.uk>
> 

Please try a bit harder.  "Reviewed-by" is neither "this matches what's 
been forever in the Amazon kernel" nor "I guarantee that Jack is a nice 
guy and doesn't screw up".  I'm sure he is but everybody screws up, and 
in this case the patch:

- does not even *apply* to the upstream kernel, because it uses 
(presumably Amazon-specific) CAP numbers above 10000

- does not work if the vCPU is moved from one physical CPU to another

- does not work if the intel_pstate driver writes to MSR_HWP_REQUEST

- does not include documentation for the new capability

- does not include a selftest

- is unacceptable anyway because, as mentioned in the cover letter, it 
isn't undone when the process exits

Jack, please understand that I am not really blaming you in any way, and 
ask some of your colleagues with upstream kernel experience (Alex Graf, 
David Woodhouse, Filippo Sironi, Jan Schoenherr, Amit Shah are the ones 
I know) which patches could be good targets for including upstream.

Paolo