linux-kernel - RE: [PATCH] clockevents/drivers/i8253: Do not zero timer counter in shutdown

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Date:   Fri, 24 Feb 2023 09:45:39 +0000
From:   "Li,Rongqing" <lirongqing@...du.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        "Michael Kelley (LINUX)" <mikelley@...rosoft.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>
CC:     KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "wei.liu@...nel.org" <wei.liu@...nel.org>,
        Dexuan Cui <decui@...rosoft.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "bp@...en8.de" <bp@...en8.de>,
        "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] clockevents/drivers/i8253: Do not zero timer counter in
 shutdown

> > > Hyper-V and KVM follow the spec, the issue that 35b69a42
> > > "(clockevents/drivers/
> > > i8253: Add support for PIT shutdown quirk") fixed is in i8253
> > > drivers, not Hyper-v, so delete the zero timer counter register in
> > > shutdown, and delete PIT shutdown quirk for Hyper-v
> >
> > From the standpoint of Hyper-V, I'm good with this change.  But
> > there's a risk that old hardware might not be compliant with the spec,
> > and needs the zero'ing for some reason. The experts in the x86 space
> > will be in the best position to assess the risk.
> 
> Yep, my feeling exactly.  My input is purely from reading those crusty old specs.

Hi Thomas:

Could you give some suggestion about this patch?

Thanks

-Li