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 68794C433EF for ; Wed, 5 Jan 2022 12:58:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236588AbiAEM6t (ORCPT ); Wed, 5 Jan 2022 07:58:49 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49510 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235965AbiAEM6p (ORCPT ); Wed, 5 Jan 2022 07:58:45 -0500 Received: from bhuna.collabora.co.uk (bhuna.collabora.co.uk [IPv6:2a00:1098:0:82:1000:25:2eeb:e3e3]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 64456C061761 for ; Wed, 5 Jan 2022 04:58:45 -0800 (PST) Received: from [127.0.0.1] (localhost [127.0.0.1]) (Authenticated sender: wlozano) with ESMTPSA id C658D1F44882 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1641387523; bh=yNIafW9es9iDBNSQ/Z9On8LylzWUxeHdxcDf8KMevu8=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Uz12lUBT86dTKzlw85feeUUvK0m1ni1+Pq8j1N7osSGPfIWbWarxgzWt5rdZVqo69 Wkv9eHV67rAtbgjdEWL3xTcaFIGJJ5KjAjTf51/p0Zn9cOZFBpArdQLHE5k5RX8xvN nB7rE6xwz7VRzVmfC/Gotb2ezNgIsMigY9aCeDo4JHpHjvEyIsTB35b08U4PplYFFs 5XfRNnDf46byemcpc7I/tbK37dG9/rh6uTCw+XKVum8ZWm6yVxBKL1+YglT1YWAfMd 6zaUPLM/UBhdBiQBKRU2ZEe7ihPzZbSVypcatR5OQSDfHPa0IeWYPV32GvDg8eeAMF jPmeu3CPdFbnA== Message-ID: <7a228120-f8fa-53ce-8857-32330968eebb@collabora.com> Date: Wed, 5 Jan 2022 09:58:36 -0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.4.0 Subject: Re: Occasional hung with UM after enable VMAP_STACK Content-Language: en-US To: Johannes Berg , linux-um@lists.infradead.org, linux-kernel@vger.kernel.org Cc: Sjoerd Simons , ritesh sarraf References: <8c26a869-0cbe-a38c-8a8d-9f3f171f7e72@collabora.com> <41fe09354fc736fb1ff2cb429e035633f24176ce.camel@sipsolutions.net> From: Walter Lozano In-Reply-To: <41fe09354fc736fb1ff2cb429e035633f24176ce.camel@sipsolutions.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Johannes, On 1/4/22 16:49, Johannes Berg wrote: > On Tue, 2022-01-04 at 16:26 -0300, Walter Lozano wrote: >> Thank you for your quick response. The Debian configuration on package >> user-mode-linux have these settings >> >> CONFIG_HAVE_ARCH_VMAP_STACK=y >> CONFIG_VMAP_STACK=y > OK, so it actually _is_ enabled. > >> as you can see in [1]. I did run some tests disabling those settings, >> which passed without any hung. >> >> Unfortunately the "occasional" behavior makes this issue a bit tricky to >> debug. >> > Right. > > Hm. I've been running our tests with it for about three months and > haven't observed any hangs, but I guess that doesn't mean much. The issue is very rare at least in my setup, I had to prepare a test environment to stress the system in order to be able to reproduce it more or less consistently. I will continue investigating and share any useful information. > To be honest, I have no particular reason to even want it, other than > that it catches accidental DMA from stack more easily ... so I guess if > we can't find anything, we might as well revert it. I hope we will be able to find the root cause of the issue. > Feels like it _should_ work though, since it's just a different location > for the stack. I see. Thank you again for your quick reply, I will keep you updated. Regards, Walter -- Walter Lozano Collabora Ltd.