linux-kernel - Re: [PATCH 0/5 V5] Avoid soft lockup message when KVM is stopped by host

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Message-ID: <20111219125217.GC3139@amit-x200.redhat.com>
Date:	Mon, 19 Dec 2011 18:22:17 +0530
From:	Amit Shah <amit.shah@...hat.com>
To:	Avi Kivity <avi@...hat.com>
Cc:	Eric B Munson <emunson@...bm.net>, mingo@...hat.com, hpa@...or.com,
	arnd@...db.de, ryanh@...ux.vnet.ibm.com, aliguori@...ibm.com,
	mtosatti@...hat.com, jeremy.fitzhardinge@...rix.com,
	levinsasha928@...il.com, Jan Kiszka <jan.kiszka@...mens.com>,
	kvm@...r.kernel.org, linux-arch@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/5 V5] Avoid soft lockup message when KVM is stopped by
 host

On (Thu) 15 Dec 2011 [13:55:15], Avi Kivity wrote:
> On 12/08/2011 01:34 PM, Amit Shah wrote:
> > On (Mon) 05 Dec 2011 [15:18:59], Eric B Munson wrote:
> > > When a guest kernel is stopped by the host hypervisor it can look like a soft
> > > lockup to the guest kernel.  This false warning can mask later soft lockup
> > > warnings which may be real.  This patch series adds a method for a host
> > > hypervisor to communicate to a guest kernel that it is being stopped.  The
> > > final patch in the series has the watchdog check this flag when it goes to
> > > issue a soft lockup warning and skip the warning if the guest knows it was
> > > stopped.
> >
> > Guest S4 would need similar treatment, and I think the code in the two
> > approaches can be shared.  Just something to consider.
> >
> 
> Why does S4 need any treatment?  The guest is aware that it's sleeping,
> unlike the other cases treated here.

Er, right.

S4 needs some treatment, though, as resume after s4 doesn't work with
kvmclock enabled.  I didn't realise this series was only handling the
soft lockup case.

		Amit
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