From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anthony Liguori 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> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from e5.ny.us.ibm.com ([32.97.182.145]:60413 "EHLO e5.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751974Ab1LNOuo (ORCPT ); Wed, 14 Dec 2011 09:50:44 -0500 Received: from /spool/local by e5.ny.us.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 14 Dec 2011 09:50:43 -0500 In-Reply-To: <4EE8B53C.6070502@redhat.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Avi Kivity Cc: Marcelo Tosatti , Eric B Munson , mingo@redhat.com, hpa@zytor.com, arnd@arndb.de, ryanh@linux.vnet.ibm.com, jeremy.fitzhardinge@citrix.com, levinsasha928@gmail.com, Jan Kiszka , kvm@vger.kernel.org, linux-arch@vger.kernel.org, x86@kernel.org, linux-kernel@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 >