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 B0B49C4332F for ; Wed, 16 Nov 2022 16:16:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232762AbiKPQQ3 (ORCPT ); Wed, 16 Nov 2022 11:16:29 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53488 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233991AbiKPQQ0 (ORCPT ); Wed, 16 Nov 2022 11:16:26 -0500 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6AC32D135 for ; Wed, 16 Nov 2022 08:16:25 -0800 (PST) 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 ams.source.kernel.org (Postfix) with ESMTPS id 1CFD1B81DE0 for ; Wed, 16 Nov 2022 16:16:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7BB8EC433C1; Wed, 16 Nov 2022 16:16:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1668615382; bh=VuCtC4r5rO4v5LPmAf61/aocsA7ivweRS0+kvCJ2oIs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=ODk9UlAYGLYxEAECTGQ6TqvD/DAIlHdnfrqVlqAgkVGEP6AAGubJ/A3oYNyjTMuIR u4krZydeXlDCZg4OuGn9wz81a4H2RQ8sGt5CqVy7BbMBss22VWlhGBbCJui/Wrx2d3 IQS0qc5QeW7jGkLmNP2RqWol+w4K+2ulNSqZMJWQ= Date: Wed, 16 Nov 2022 17:16:20 +0100 From: Greg Kroah-Hartman To: Andy Shevchenko Cc: linux-kernel@vger.kernel.org, Fei Li , "Rafael J. Wysocki" Subject: Re: [PATCH v4 1/1] virt: acrn: Mark the uuid field as unused Message-ID: References: <20221116092254.66234-1-andriy.shevchenko@linux.intel.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 Wed, Nov 16, 2022 at 06:04:37PM +0200, Andy Shevchenko wrote: > On Wed, Nov 16, 2022 at 04:20:08PM +0100, Greg Kroah-Hartman wrote: > > On Wed, Nov 16, 2022 at 03:29:31PM +0200, Andy Shevchenko wrote: > > > On Wed, Nov 16, 2022 at 12:42:16PM +0100, Greg Kroah-Hartman wrote: > > > > On Wed, Nov 16, 2022 at 11:22:54AM +0200, Andy Shevchenko wrote: > > ... > > > > > > - * @uuid: UUID of the VM. Pass to hypervisor directly. > > > > > + * @uuid: Reserved (used to be UUID of the VM) > > > > > > > > If it's reserved, then don't you need to check for 0? > > > > > > Reserved in a way that it may content something we just don't care about. > > > > "reserved" in the kernel ioctls mean "must be 0 and we will test for it, > > otherwise this is an empty/useless field that can never be touched again > > in the future. > > > > Please spell it out in detail as to if you can ever use this later on, > > and what the kernel will do (if anything) if it is set. > > > > And if "the kernel ignores it" then that means these bytes are now > > "empty space never to be used again", right? > > Right, I will fix this in v5. > > ... > > > > > > + __u8 uuid[16]; > > > > > > > > You just changed the type here, so what is that going to break in > > > > userspace that depended on this being of a structure type and now it's > > > > an array? > > > > > > It's the same. The previous was hidden behind additional type level. > > > > Same size, yes. Same C structure definition, no. > > It doesn't matter, see below. > > > > > And no other kernel changes needed? Shouldn't you warn if this field is > > > > set? > > > > > > No, as pointed out in the commit message kernel never ever used this. > > > > That does not mean that userspace tools never did, right? You are > > changing the structure definition, what tool just broke? > > The only tool has been amended like a year ago, so the answer is none. > The commit message has links to the commits in question that made that > amendment. > > Maybe I should remove Fixes tags? In such case we will very much know > that no old tools will be run on the new kernel. Please remove "fixes" as this doesn't "fix" anything. thanks, greg k-h