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 lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id E350EC433F5 for ; Tue, 11 Jan 2022 11:02:33 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.255682.438173 (Exim 4.92) (envelope-from ) id 1n7Eun-00055v-9r; Tue, 11 Jan 2022 11:02:09 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 255682.438173; Tue, 11 Jan 2022 11:02:09 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1n7Eun-00055o-6X; Tue, 11 Jan 2022 11:02:09 +0000 Received: by outflank-mailman (input) for mailman id 255682; Tue, 11 Jan 2022 11:02:07 +0000 Received: from se1-gles-sth1-in.inumbo.com ([159.253.27.254] helo=se1-gles-sth1.inumbo.com) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1n7Eul-00055i-RF for xen-devel@lists.xenproject.org; Tue, 11 Jan 2022 11:02:07 +0000 Received: from smarthost01c.sbp.mail.zen.net.uk (smarthost01c.sbp.mail.zen.net.uk [212.23.1.5]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id e9ea95a9-72cd-11ec-9ce5-af14b9085ebd; Tue, 11 Jan 2022 12:02:06 +0100 (CET) Received: from [82.70.146.41] (helo=pear.davidvrabel.org.UK) by smarthost01c.sbp.mail.zen.net.uk with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1n7Euj-0005Al-C4; Tue, 11 Jan 2022 11:02:05 +0000 Received: from apple.davidvrabel.org.uk ([82.70.146.43]) by pear.davidvrabel.org.uk with esmtp (Exim 4.92) (envelope-from ) id 1n7Eua-0001xq-VD; Tue, 11 Jan 2022 11:02:04 +0000 X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: e9ea95a9-72cd-11ec-9ce5-af14b9085ebd Message-ID: Date: Tue, 11 Jan 2022 11:01:55 +0000 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.4.1 Content-Language: en-GB To: Stefano Stabellini , Julien Grall Cc: xen-devel@lists.xenproject.org, Bertrand.Marquis@arm.com, Luca Miccio , Stefano Stabellini , Volodymyr Babchuk , Andrew Cooper , Jan Beulich , George Dunlap , Wei Liu , Juergen Gross References: <20220108004912.3820176-1-sstabellini@kernel.org> <580a888e-24c4-5d16-8c70-f3d7b34ac2c9@xen.org> From: David Vrabel In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-SA-Exim-Connect-IP: 82.70.146.43 X-SA-Exim-Mail-From: dvrabel@cantab.net Subject: Re: [XEN PATCH 1/7] xen: introduce XENFEAT_xenstore_late_init X-SA-Exim-Version: 4.2.1 (built Wed, 08 May 2019 21:11:16 +0000) X-SA-Exim-Scanned: Yes (on pear.davidvrabel.org.uk) X-Originating-smarthost01c-IP: [82.70.146.41] Feedback-ID: 82.70.146.41 On 10/01/2022 22:55, Stefano Stabellini wrote: > > I have a patch for Linux that if XENFEAT_xenstore_late_init is present > makes Linux wait for an event notification before initializing xenstore: > https://marc.info/?l=xen-devel&m=164160299315589 > > So with v1 of the Xen and Linux patches series: > - Xen allocates the event channel at domain creation > - Linux boots, sees XENFEAT_xenstore_late_init and wait for an event > - init-dom0less later allocates the xenstore page > - init-dom0less triggers the xenstore event channel > - Linux receives the event and finishes the initialization, including > mapping the xenstore page You can get this behaviour without the new feature. - Xen allocates the event channel at domain creation - Linux boots, sees HVM_PARAM_STORE_PFN is invalid and there's a xenstore event channel and waits for an event - init-dom0less later allocates the xenstore page - init-dom0less triggers the xenstore event channel - Linux receives the event and finishes the initialization, including mapping the xenstore page- David