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

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Message-ID: <ZqzzVRQYCmUwD0OL@google.com>
Date: Fri, 2 Aug 2024 07:55:17 -0700
From: Sean Christopherson <seanjc@...gle.com>
To: David Woodhouse <dwmw2@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>, Michael Kelley <mhklinux@...look.com>, 
	"lirongqing@...du.com" <lirongqing@...du.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 Fri, Aug 02, 2024, David Woodhouse wrote:
> On Thu, 2024-08-01 at 20:54 +0200, Thomas Gleixner wrote:
> > On Thu, Aug 01 2024 at 16:14, Michael Kelley wrote:
> > > I don't have a convenient way to test my sequence on KVM.
> > 
> > But still fails in KVM
> 
> By KVM you mean the in-kernel one that we want to kill because everyone
> should be using userspace IRQ chips these days?

What exactly do you want to kill?  In-kernel local APIC obviously needs to stay
for APICv/AVIC.

And IMO, encouraging userspace I/O APIC emulation is a net negative for KVM and
the community as a whole, as the number of VMMs in use these days results in a
decent amount of duplicated work in userspace VMMs, especially when accounting
for hardware and software quirks.