linux-kernel - RE: [PATCH v2] x86/acrn: Set X86_FEATURE_TSC_KNOWN

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Message-ID: <SJ1PR11MB615392FC28992FD088E05046BF0A9@SJ1PR11MB6153.namprd11.prod.outlook.com>
Date:   Mon, 21 Nov 2022 07:52:23 +0000
From:   "Li, Fei1" <fei1.li@...el.com>
To:     Borislav Petkov <bp@...en8.de>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "peterz@...radead.org" <peterz@...radead.org>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "hpa@...or.com" <hpa@...or.com>, "Wang, Yu1" <yu1.wang@...el.com>,
        "Chen, Conghui" <conghui.chen@...el.com>,
        "Yin, Fengwei" <fengwei.yin@...el.com>,
        "Mao, Junjie" <junjie.mao@...el.com>
Subject: RE: [PATCH v2] x86/acrn: Set X86_FEATURE_TSC_KNOWN_FREQ

> Hi Borislav
>
> Thanks for your comments. So sorry to reply you late.
>
> >
> > What if the HV has unstable TSCs? How do you handle that?
> >
> ACRN hypervisor assumes:
> a) The TSC runs at a constant rate in all ACPI P-, C-. and T-states (i.e. invariant TSC)
> b) The invariant TSC is based on only one invariant timekeeping hardware (called
>    Always Running Timer or ART). ACRN main target uses for IoT devices
>    which are typically one-socket
> c) ACRN lives with temperature influence on TSC frequency
>
Hi Borislav

Kindly ping for any comments here ?