linux-kernel - Re: [PATCH 1/2] i8253: Disable PIT timer 0 when not in use

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Message-ID: <c444e22855305bc9d335dc1623fdd7ec0cb35c02.camel@infradead.org>
Date: Fri, 02 Aug 2024 17:01:40 +0100
From: David Woodhouse <dwmw2@...radead.org>
To: Michael Kelley <mhklinux@...look.com>, "tglx@...utronix.de"
	 <tglx@...utronix.de>, "x86@...nel.org" <x86@...nel.org>
Cc: "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>, 
 "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Daniel
 Lezcano <daniel.lezcano@...aro.org>
Subject: Re: [PATCH 1/2] i8253: Disable PIT timer 0 when not in use

On Fri, 2024-08-02 at 15:44 +0000, Michael Kelley wrote:
> Did a basic smoke test of this two-patch series on a Hyper-V Gen 1
> VM and on a Gen 2 VM. All looks good and behaves as expected.
> 
> On the Gen 1 VM, the PIT is used briefly at boot (takes ~35 interrupts)
> before the Hyper-V synthetic timer takes over and the PIT is shutdown.
> As expected, no further interrupts are received from the PIT.
> 
> On a Gen 2 VM, apic_needs_pit() returns true because
> X86_FEATURE_ARAT isn't present. The PIT doesn't exist in a
> Gen 2 VM, but the code paths handle this situation with no
> problems, just as before the patch series.
> 
> For the two-patch series on Hyper-V,
> Tested-by: Michael Kelley <mhkelley@...look.com>

Thank you!

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