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 9BD5CC6FD18 for ; Wed, 29 Mar 2023 17:51:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229649AbjC2Rvn (ORCPT ); Wed, 29 Mar 2023 13:51:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45610 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229650AbjC2Rvl (ORCPT ); Wed, 29 Mar 2023 13:51:41 -0400 X-Greylist: delayed 462 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Wed, 29 Mar 2023 10:51:32 PDT Received: from forward500a.mail.yandex.net (forward500a.mail.yandex.net [IPv6:2a02:6b8:c0e:500:1:45:d181:d500]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7DB911FC0; Wed, 29 Mar 2023 10:51:32 -0700 (PDT) Received: from mail-nwsmtp-smtp-production-main-51.vla.yp-c.yandex.net (mail-nwsmtp-smtp-production-main-51.vla.yp-c.yandex.net [IPv6:2a02:6b8:c1f:5e51:0:640:23ee:0]) by forward500a.mail.yandex.net (Yandex) with ESMTP id 9980C5EEAE; Wed, 29 Mar 2023 20:43:46 +0300 (MSK) Received: by mail-nwsmtp-smtp-production-main-51.vla.yp-c.yandex.net (smtp/Yandex) with ESMTPSA id dhMcaO4DV4Y0-RpmWL4SQ; Wed, 29 Mar 2023 20:43:45 +0300 X-Yandex-Fwd: 1 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=yandex.ru; s=mail; t=1680111825; bh=+6hq+ziRMggGufmRgWE7w5d122tdGKys5kWzuZKVUlY=; h=From:In-Reply-To:Cc:Date:References:To:Subject:Message-ID; b=ocAFkHsKYq8hDDFbwOSDcQx9ejam55BOvIe2gdGzNi5HwmrEEMlYgq2q60zb06+5p OxL/e8/xRGTmNB+nfCI3Sokiy9iscLolRhuUUZ9W/hBjqyEnqDSZZVl3U38LBVg1Op NxTgxhatiACTTX/30DtkJgcbsT4eTpL2sU9ewG7M= Authentication-Results: mail-nwsmtp-smtp-production-main-51.vla.yp-c.yandex.net; dkim=pass header.i=@yandex.ru Message-ID: <0994ea3a-e197-e938-6eab-72433d6547fd@yandex.ru> Date: Wed, 29 Mar 2023 22:43:38 +0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.7.1 Subject: Re: [PATCH 6.0.y / 6.1.y] x86/split_lock: Add sysctl to control the misery mode Content-Language: en-US To: Sean Christopherson , "Guilherme G. Piccoli" Cc: Peter Zijlstra , Greg KH , stable@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, corbet@lwn.net, kernel-dev@igalia.com, kernel@gpiccoli.net, fenghua.yu@intel.com, joshua@froggi.es, pgofman@codeweavers.com, pavel@denx.de, pgriffais@valvesoftware.com, zfigura@codeweavers.com, cristian.ciocaltea@collabora.com, Thomas Gleixner , Dave Hansen , Tony Luck , Andre Almeida References: <20221218234400.795055-1-gpiccoli@igalia.com> <3ff9f56c-479b-2dbd-9ee6-c7d00c7bd285@igalia.com> From: stsp In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Sean, thanks for a head-up! 29.03.2023 22:14, Sean Christopherson пишет: > Resurrecting this thread with a concrete use case. > dosemu2, which uses KVM to accelerate DOS emulation (stating the obvious), ran > into a problem where the hardcoded (prior to this patch) behavior will effectively > hang userspace if the 10ms sleep is interrupted, e.g. by a periodic SIGALRM[*]. Yes, and we also created a ready-to-use host test-case with no dosemu2 involved. > Alternatively, we could try to figure out a way to ensure forward progress without > letting userpace run an end-around on the enforced misery, but backporting this > patch to stable kernels seems easier. > > Stas, do you happen to know what the oldest stable kernel your users use, i.e. > how far back this backport would need to go? It seems, the "broken" code was added by the patch b041b525dab95 which is "described" as v5.18-rc4-1-gb041b525dab9. So I guess the answer would be "down to 5.18". Of course I don't believe the patch you mention, is a real solution. Its good for -stable, but something else needs to be developed in the future.