From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E50D9C43217 for ; Fri, 29 Apr 2022 09:39:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1356669AbiD2JmU (ORCPT ); Fri, 29 Apr 2022 05:42:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:47534 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1356614AbiD2JmO (ORCPT ); Fri, 29 Apr 2022 05:42:14 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C2D81BC879; Fri, 29 Apr 2022 02:38:56 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 2F45962269; Fri, 29 Apr 2022 09:38:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0ED33C385A4; Fri, 29 Apr 2022 09:38:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1651225135; bh=7wQ6VFKp/al5aiAM5L8qP/IgOcL9rHjqdl9Sb4sPKwA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=u2DbfNQ45vxveL0XtmTG+CKMjygaqgD8Av0W6Kuw+VJ5e+DYDWKJCIGvORHScfh88 iOaoWBEB7wOFUBnM32SqMwumKX4AAc65EApor5VRNyd3szCKI2Oli1y9B8/Aue3YEK mT2GYzXYKkLbWiopnuKH89/cQU4e8m+wfzfw22Rk= Date: Fri, 29 Apr 2022 11:38:52 +0200 From: Greg Kroah-Hartman To: Sebastian Ene Cc: linux-kernel@vger.kernel.org, Derek Kiernan , Dragan Cvetic , Arnd Bergmann , devicetree@vger.kernel.org, qperret@google.com, will@kernel.org, Rob Herring , Guenter Roeck Subject: Re: [PATCH v4 2/2] misc: Add a mechanism to detect stalls on guest vCPUs Message-ID: References: <20220429083030.3241640-1-sebastianene@google.com> <20220429083030.3241640-3-sebastianene@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Apr 29, 2022 at 09:26:26AM +0000, Sebastian Ene wrote: > On Fri, Apr 29, 2022 at 10:51:14AM +0200, Greg Kroah-Hartman wrote: > > On Fri, Apr 29, 2022 at 08:30:33AM +0000, Sebastian Ene wrote: > > > This driver creates per-cpu hrtimers which are required to do the > > > periodic 'pet' operation. On a conventional watchdog-core driver, the > > > userspace is responsible for delivering the 'pet' events by writing to > > > the particular /dev/watchdogN node. In this case we require a strong > > > thread affinity to be able to account for lost time on a per vCPU. > > > > > > This part of the driver is the 'frontend' which is reponsible for > > > delivering the periodic 'pet' events, configuring the virtual peripheral > > > and listening for cpu hotplug events. The other part of the driver > > > handles the peripheral emulation and this part accounts for lost time by > > > looking at the /proc/{}/task/{}/stat entries and is located here: > > > https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3548817 > > > > > > Signed-off-by: Sebastian Ene > > > --- > > > drivers/misc/Kconfig | 12 +++ > > > drivers/misc/Makefile | 1 + > > > drivers/misc/vm-watchdog.c | 206 +++++++++++++++++++++++++++++++++++++ > > > 3 files changed, 219 insertions(+) > > > create mode 100644 drivers/misc/vm-watchdog.c > > > > > > diff --git a/drivers/misc/Kconfig b/drivers/misc/Kconfig > > > index 2b9572a6d114..26c3a99e269c 100644 > > > --- a/drivers/misc/Kconfig > > > +++ b/drivers/misc/Kconfig > > > @@ -493,6 +493,18 @@ config OPEN_DICE > > > > > > If unsure, say N. > > > > > > +config VM_WATCHDOG > > > + tristate "Virtual Machine Watchdog" > > > + select LOCKUP_DETECTOR > > > + help > > > + Detect CPU locks on the virtual machine. This driver relies on the > > > + hrtimers which are CPU-binded to do the 'pet' operation. When a vCPU > > > + has to do a 'pet', it exits the guest through MMIO write and the > > > + backend driver takes into account the lost ticks for this particular > > > + CPU. > > Hi, > > > > > There's nothing to keep this tied to a virtual machine at all, right? > > You are just relying on some iomem address to be updated, so it should > > be a "generic_iomem_watchdog" driver as there's nothing specific to vms > > at all from what I can tell. > > > > thanks, > > > > greg k-h > > That's right although I might think of using the term "generic lockup detector" > instead of watchdog. The only reason why I would keep "virtual machine" > word in, is that there is no actual hardware for this. That doesn't really matter, it's just a memory location in device tree that you are needing, odds are some hardware device could use it just like this. thanks, greg k-h