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

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Message-ID: <87o76c2hw2.ffs@tglx>
Date: Thu, 01 Aug 2024 20:54:37 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Michael Kelley <mhklinux@...look.com>, "lirongqing@...du.com"
 <lirongqing@...du.com>, "seanjc@...gle.com" <seanjc@...gle.com>,
 "kys@...rosoft.com" <kys@...rosoft.com>, "haiyangz@...rosoft.com"
 <haiyangz@...rosoft.com>, "wei.liu@...nel.org" <wei.liu@...nel.org>,
 "decui@...rosoft.com" <decui@...rosoft.com>, "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

On Thu, Aug 01 2024 at 16:14, Michael Kelley wrote:
> From: Thomas Gleixner <tglx@...utronix.de> Sent: Thursday, August 1, 2024 7:21 AM
> FWIW, in Hyper-V guests with the Hyper-V quirk removed, tglx's new
> sequence does *not* stop the PIT. But this sequence does:
>
> outb_p(0x30, PIT_MODE);
> outb_p(0xff, PIT_CH0);
> outb_p(0xff, PIT_CH0);
>
> outb_p(0x30, PIT_MODE);
> outb_p(0xff, PIT_CH0);

That works on bare metal too

> I don't have a convenient way to test my sequence on KVM.

But still fails in KVM

Thanks,

        tglx