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 00BC6C433EF for ; Sat, 30 Apr 2022 06:18:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S241357AbiD3GVs (ORCPT ); Sat, 30 Apr 2022 02:21:48 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45354 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229770AbiD3GVq (ORCPT ); Sat, 30 Apr 2022 02:21:46 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B970ACFB8C; Fri, 29 Apr 2022 23:18:24 -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 F12E460A28; Sat, 30 Apr 2022 06:18:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9AD55C385AA; Sat, 30 Apr 2022 06:18:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1651299503; bh=uYF2s/xQF4T6AlR6mb0JRgmAFtb0jfMpWbE35bo1HwU=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=2BQcS/4NH+9ysls92X0SSlMU05RTtCM3xnAEHjDjzcWSOmFuV9GpH39yV9EC6WDyn rYjTAhmhtnXik1cjo64wcxr4gxnmY32CXfbLqPHcxoEwfikfFZutcJacNREFh2olqH giURfq009PrksK7aWDe/vXUbWBgFCAsvr8YuvCM0= Date: Sat, 30 Apr 2022 08:18:14 +0200 From: Greg Kroah-Hartman To: Guenter Roeck Cc: Sebastian Ene , Rob Herring , Arnd Bergmann , Dragan Cvetic , linux-kernel@vger.kernel.org, devicetree@vger.kernel.org, maz@kernel.org, will@kernel.org, qperret@google.com 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 09:51:51AM -0700, Guenter Roeck wrote: > On 4/29/22 01:48, 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. > > > + To compile this driver as a module, choose M here: the > > > + module will be called vm-wdt. > > > > You forgot to name the module properly here based on the Makefile change > > you made. > > > > And again, as this is called a "watchdog", it seems crazy that it is not > > in drivers/watchdog/ > > > > I disagree. It is not a watchdog driver in the traditional sense (it does > not use, want to use, or need to use the watchdog driver API or ABI). > Its functionality is similar to the functionality of kernel/watchdog.c, > which doesn't belong into drivers/watchdog either. Ah, ok, that makes more sense, the user/kernel api is not the same. Someone should put that in the changelog next time :) thanks, greg k-h