From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755810Ab1H3QhR (ORCPT ); Tue, 30 Aug 2011 12:37:17 -0400 Received: from mail-bw0-f46.google.com ([209.85.214.46]:38599 "EHLO mail-bw0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755763Ab1H3QhP convert rfc822-to-8bit (ORCPT ); Tue, 30 Aug 2011 12:37:15 -0400 MIME-Version: 1.0 In-Reply-To: <20110830122630.GA19450@amt.cnet> References: <1314660435-23293-1-git-send-email-emunson@mgebm.net> <20110830122630.GA19450@amt.cnet> Date: Tue, 30 Aug 2011 10:37:13 -0600 Message-ID: Subject: Re: [PATCH 0/4] Avoid soft lockup message when KVM is stopped by host From: Eric B Munson To: Marcelo Tosatti Cc: avi@redhat.com, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, arnd@arndb.de, riel@redhat.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, kvm-ppc@vger.kernel.org, aliguori@us.ibm.com, raharper@us.ibm.com, kvm-ia64@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Aug 30, 2011 at 06:26, Marcelo Tosatti wrote: > On Mon, Aug 29, 2011 at 05:27:11PM -0600, Eric B Munson wrote: >> Currently, when qemu stops a guest kernel that guest will issue a soft lockup >> message when it resumes.  This set provides the ability for qemu to comminucate >> to the guest that it has been stopped.  When the guest hits the watchdog on >> resume it will check if it was suspended before issuing the warning. >> >> Eric B Munson (4): >>   Add flag to indicate that a vm was stopped by the host >>   Add functions to check if the host has stopped the vm >>   Add generic stubs for kvm stop check functions >>   Add check for suspended vm in softlockup detector >> >>  arch/x86/include/asm/pvclock-abi.h |    1 + >>  arch/x86/include/asm/pvclock.h     |    2 ++ >>  arch/x86/kernel/kvmclock.c         |   14 ++++++++++++++ >>  include/asm-generic/pvclock.h      |   14 ++++++++++++++ >>  kernel/watchdog.c                  |   12 ++++++++++++ >>  5 files changed, 43 insertions(+), 0 deletions(-) >>  create mode 100644 include/asm-generic/pvclock.h >> >> -- >> 1.7.4.1 > > How is the host supposed to set this flag? The hypervisor will set the flag (the second bit in the struct pvclock_vcpu_time_info.flags field) when it stops the guest. I could be reading pvclock-abi.h incorrectly, but the way I understand it is that this structure is used to communicate between hypervisor and guest. > > As mentioned previously, if you save save/restore the offset added to > kvmclock on stop/cont (and the TSC MSR, forgot to mention that), no > paravirt infrastructure is required. Which means the issue is also fixed > for older guests. >