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 1E768C433F5 for ; Tue, 11 Jan 2022 22:52:23 +0000 (UTC) Received: from list by lists.xenproject.org with outflank-mailman.256175.439499 (Exim 4.92) (envelope-from ) id 1n7Pzx-0005kJ-3B; Tue, 11 Jan 2022 22:52:13 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 256175.439499; Tue, 11 Jan 2022 22:52:13 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1n7Pzx-0005kC-0A; Tue, 11 Jan 2022 22:52:13 +0000 Received: by outflank-mailman (input) for mailman id 256175; Tue, 11 Jan 2022 22:52:11 +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 1n7Pzv-0005jI-Lh for xen-devel@lists.xenproject.org; Tue, 11 Jan 2022 22:52:11 +0000 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by se1-gles-sth1.inumbo.com (Halon) with ESMTPS id 1bebab76-7331-11ec-9ce5-af14b9085ebd; Tue, 11 Jan 2022 23:52:10 +0100 (CET) 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 BDC4B61351; Tue, 11 Jan 2022 22:52:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id A10C1C36AE3; Tue, 11 Jan 2022 22:52:08 +0000 (UTC) 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: 1bebab76-7331-11ec-9ce5-af14b9085ebd DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1641941529; bh=EW7LVEUPxDyYGzWedxB8FFH2ZaZhIR9fF+MZ94tFwDM=; h=Date:From:To:cc:Subject:In-Reply-To:References:From; b=JmAJ6nbzWVvFl/2XFUKqqV+7wrAC8o8VlvHUOcPe1oRd10MRAYRfHqQuHo2i3V5Fe vQI/X4UnCUjxmHvqC2TizkauHIfGOUld8aUwAj8PmI0j7/SMidfcjcgLnig21ty7er UzFjtxUqvT8HDQmLJyNQvMAu2NtSmIJMajzNTFTolJmSLmJvPdzweS8V53Xkzq9BIP kxSJpodv2hCcYPSubSeJjnAqgPJuD2XwrVws6dSzciEtEqK6KjvbRx2Gf257LOSWmG 75Ke3rJBjOJLiwR8TwuxfwiKTTRuf5UaNrvwwnAzuUWd8mBK5awug7RLgk0AOPpWim fz8ft1bBjNM+A== Date: Tue, 11 Jan 2022 14:52:08 -0800 (PST) From: Stefano Stabellini X-X-Sender: sstabellini@ubuntu-linux-20-04-desktop To: David Vrabel cc: Stefano Stabellini , Julien Grall , 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 Subject: Re: [XEN PATCH 1/7] xen: introduce XENFEAT_xenstore_late_init In-Reply-To: Message-ID: References: <20220108004912.3820176-1-sstabellini@kernel.org> <580a888e-24c4-5d16-8c70-f3d7b34ac2c9@xen.org> User-Agent: Alpine 2.22 (DEB 394 2020-01-19) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII On Tue, 11 Jan 2022, David Vrabel wrote: > 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- Hey David! Yes, this is similar to what I had in mind and I managed to make it work successfully.