linux-kernel - Re: [PATCH v2 2/3] KVM: X86: Provide a capability to disable cstate msr read intercepts

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Message-ID: <b30067df-2929-9ce9-221f-0f1a84dd1228@redhat.com>
Date:   Tue, 11 Jun 2019 13:09:53 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Wanpeng Li <kernellwp@...il.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Liran Alon <liran.alon@...cle.com>
Subject: Re: [PATCH v2 2/3] KVM: X86: Provide a capability to disable cstate
 msr read intercepts

On 11/06/19 09:38, Wanpeng Li wrote:
> MSR_CORE_C1_RES is unreadable except for ATOM platform, so I think we
> can avoid the complex logic to handle C1 now. :)

I disagree.  Linux uses it on all platforms is available, and virtual
machines that don't pass mwait through _only_ have C1, so it would be
less useful to have deep C-state residency MSRs and not C1 residency.

But turbostat can get the information from sysfs, so what are these MSRs
used for?

Paolo