linux-kernel - Re: [RFC PATCH 0/3] Avoid soft lockup message when KVM is stopped by host

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Message-ID: <4E3A5A38.9080406@redhat.com>
Date:	Thu, 04 Aug 2011 11:37:12 +0300
From:	Dor Laor <dlaor@...hat.com>
To:	Eric B Munson <emunson@...bm.net>
CC:	kvm@...r.kernel.org, kvm-ia64@...r.kernel.org,
	kvm-ppc@...r.kernel.org, avi@...hat.com, riel@...hat.com,
	glommer@...hat.com, linux-kernel@...r.kernel.org,
	aliguori@...ibm.com, raharper@...ibm.com,
	Glauber Costa <glommer@...il.com>
Subject: Re: [RFC PATCH 0/3] Avoid soft lockup message when KVM is stopped
 by host

On 08/03/2011 05:24 PM, Eric B Munson wrote:
> This set is just a rough first pass at avoiding soft lockup warnings when a host
> pauses the execution of a guest.  A flag is set by the host in the shared page
> used for the pvclock when the host goes to stop the guest.  When the guest
> resumes and detects a soft lockup, this flag is checked and cleared and the soft
> lockup message is skipped.

While this will cover the case were the host stops a guest, there will 
be other plain cases where the host is just over committed and will 
cause a softlockup false positive on the guest.

Softlockup should use stolen time that makes use of the guest running 
info would cover both cases

>
> This currently breaks the build for non-x86 architectures but part of what I am
> looking for here is how to go about adding the function stubs for everything
> else.
>
> Eric B Munson (3):
>    Add flag to indicate that a vm was stopped by the host
>    Add functions to check if the host has stopped the vm
>    Add check for suspended vm in softlockup detector
>
>   arch/x86/include/asm/pvclock-abi.h |    1 +
>   arch/x86/include/asm/pvclock.h     |    3 +++
>   arch/x86/kernel/kvmclock.c         |   12 ++++++++++++
>   kernel/watchdog.c                  |   11 +++++++++++
>   4 files changed, 27 insertions(+), 0 deletions(-)
>

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