From: Wanpeng Li <kernellwp@gmail.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: LKML <linux-kernel@vger.kernel.org>, kvm <kvm@vger.kernel.org>,
"Radim Krčmář" <rkrcmar@redhat.com>,
"Sean Christopherson" <sean.j.christopherson@intel.com>,
"Liran Alon" <liran.alon@oracle.com>
Subject: Re: [PATCH v2 2/3] KVM: X86: Provide a capability to disable cstate msr read intercepts
Date: Tue, 11 Jun 2019 19:35:11 +0800 [thread overview]
Message-ID: <CANRm+Cy+BVHeXjfSPhPz=n7_Qg8oQEC8DdcpCzEV5v4qYXgJGw@mail.gmail.com> (raw)
In-Reply-To: <b30067df-2929-9ce9-221f-0f1a84dd1228@redhat.com>
On Tue, 11 Jun 2019 at 19:09, Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> 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?
The sysfs is not accurate, the time which is accumulated in the
function cpuidle_enter_state() is the expected cstate we hope to enter
instead of the real cstate we finally enter. For example, we found
several SKX/CLX models can't enter deeper cstates in non-root mode,
Intel hardware team has been working on this according to our report
recently. The bare-metal cstate residency msrs don't increase in
non-root mode, however, the time under
/sys/devices/system/cpu/cpux/cpuidle/statex/ increase gradually in the
guest.
Regards,
Wanpeng Li
next prev parent reply other threads:[~2019-06-11 11:34 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-21 6:06 [PATCH 1/3] KVM: Documentation: Add disable pause exits to KVM_CAP_X86_DISABLE_EXITS Wanpeng Li
2019-05-21 6:06 ` [PATCH v2 2/3] KVM: X86: Provide a capability to disable cstate msr read intercepts Wanpeng Li
2019-06-04 16:53 ` Paolo Bonzini
2019-06-05 10:56 ` Wanpeng Li
2019-06-11 7:38 ` Wanpeng Li
2019-06-11 11:09 ` Paolo Bonzini
2019-06-11 11:35 ` Wanpeng Li [this message]
2019-06-12 2:20 ` Wanpeng Li
2019-05-21 6:06 ` [PATCH v2 3/3] KVM: X86: Emulate MSR_IA32_MISC_ENABLE MWAIT bit Wanpeng Li
2019-06-04 16:59 ` Paolo Bonzini
2019-06-05 11:00 ` Wanpeng Li
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