From mboxrd@z Thu Jan  1 00:00:00 1970
From: Anthony Liguori <aliguori@us.ibm.com>
Subject: Re: [PATCH 0/5 V5] Avoid soft lockup message when KVM is stopped
 by host
Date: Wed, 14 Dec 2011 08:49:51 -0600
Message-ID: <4EE8B78F.9090104@us.ibm.com>
References: <1323116344-17911-1-git-send-email-emunson@mgebm.net>	<4EDF7B0D.4060001@redhat.com> <20111214121622.GB18317@amt.cnet> <4EE8B53C.6070502@redhat.com>
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Cc: Marcelo Tosatti <mtosatti@redhat.com>,
	Eric B Munson <emunson@mgebm.net>, mingo@redhat.com,
	hpa@zytor.com, arnd@arndb.de, ryanh@linux.vnet.ibm.com,
	jeremy.fitzhardinge@citrix.com, levinsasha928@gmail.com,
	Jan Kiszka <jan.kiszka@siemens.com>, kvm@vger.kernel.org,
	linux-arch@vger.kernel.org, x86@kernel.org,
	linux-kernel@vger.kernel.org
To: Avi Kivity <avi@redhat.com>
Return-path: <linux-arch-owner@vger.kernel.org>
In-Reply-To: <4EE8B53C.6070502@redhat.com>
Sender: linux-arch-owner@vger.kernel.org
List-Id: kvm.vger.kernel.org

On 12/14/2011 08:39 AM, Avi Kivity wrote:
> On 12/14/2011 02:16 PM, Marcelo Tosatti wrote:
>>> Having this controlled from userspace means it doesn't work for SIGSTOP
>>> or for long scheduling delays.  What about doing this automatically
>>> based on preempt notifiers?
>>
>> Long scheduling delays should be considered hangups from the guest
>> perspective.
>
> Why?  To the guest it looks like slow hardware, but it will interpret it
> as a softlockup.
>
>> About SIGSTOP, that is a corner case. Unsure if its even properly supported
>> by QEMU.
>
> It works from my experience.

We don't adjust vm_clock's offset on SIGSTOP/SIGCONT so while it may appear to 
work okay, QEMU isn't exhibiting the behavior it is supposed to.

Regards,

Anthony Liguori

>