From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ryan Harper Subject: Re: [PATCH 0/4] Avoid soft lockup message when KVM is stopped by host Date: Tue, 30 Aug 2011 09:12:17 -0500 Message-ID: <20110830141217.GF30100@us.ibm.com> References: <1314660435-23293-1-git-send-email-emunson@mgebm.net> <20110830122630.GA19450@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20110830122630.GA19450@amt.cnet> Sender: kvm-ppc-owner@vger.kernel.org To: Marcelo Tosatti Cc: Eric B Munson , 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, Anthony Liguori , Ryan A Harper , kvm-ia64@vger.kernel.org List-Id: linux-arch.vger.kernel.org * Marcelo Tosatti [2011-08-30 07:35]: > 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? > > 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. How is saving the offset going to prevent a large jump from triggering the softlock message? Won't we still have not touched the watchdog for that long period of time? -- Ryan Harper Software Engineer; Linux Technology Center IBM Corp., Austin, Tx ryanh@us.ibm.com From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from e5.ny.us.ibm.com ([32.97.182.145]:52238 "EHLO e5.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750854Ab1H3OMj (ORCPT ); Tue, 30 Aug 2011 10:12:39 -0400 Date: Tue, 30 Aug 2011 09:12:17 -0500 From: Ryan Harper Subject: Re: [PATCH 0/4] Avoid soft lockup message when KVM is stopped by host Message-ID: <20110830141217.GF30100@us.ibm.com> References: <1314660435-23293-1-git-send-email-emunson@mgebm.net> <20110830122630.GA19450@amt.cnet> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110830122630.GA19450@amt.cnet> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Marcelo Tosatti Cc: Eric B Munson , 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, Anthony Liguori , Ryan A Harper , kvm-ia64@vger.kernel.org Message-ID: <20110830141217.s68Ck4Rw--Z3VjwpHI9bzKLo6JOOHGZf3TpUJbuP1mQ@z> * Marcelo Tosatti [2011-08-30 07:35]: > 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? > > 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. How is saving the offset going to prevent a large jump from triggering the softlock message? Won't we still have not touched the watchdog for that long period of time? -- Ryan Harper Software Engineer; Linux Technology Center IBM Corp., Austin, Tx ryanh@us.ibm.com