From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55519) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1d5XlA-0006lq-71 for qemu-devel@nongnu.org; Tue, 02 May 2017 09:22:33 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1d5Xl6-00011e-Ux for qemu-devel@nongnu.org; Tue, 02 May 2017 09:22:32 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47292) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1d5Xl6-00011U-LR for qemu-devel@nongnu.org; Tue, 02 May 2017 09:22:28 -0400 References: <1493719600-30853-1-git-send-email-thuth@redhat.com> <52fc3efd-55a7-af2d-ce8c-9b4565dfe6dc@de.ibm.com> From: Paolo Bonzini Message-ID: Date: Tue, 2 May 2017 15:22:22 +0200 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] Deprecate '-enable-kvm' and '-enable-hax' in favour of '-accel' List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Christian Borntraeger , Thomas Huth , qemu-devel@nongnu.org Cc: Vincent Palatin On 02/05/2017 12:48, Christian Borntraeger wrote: >> I'm aware of the fact that likely a lot of users are still using >> -enable-kvm, and I did not mean that we should remove it soon yet. But >> IMHO we should start now to inform the users that they should slowly >> switch to the better option "-accel" instead, so that we could maybe >> remove this "-enable-xxx" stuff sometime in the distant future (let's >> say QEMU v4.0?). > > I come from the Linux side, where "breaking a working setup" will result in > an angry Linus. We certainly have not such strict rules here and we could > base the decision on the question "how expensive is the maintenance > of this option?". I think marking it as "legacy option" is fine, but I doubt > that removing it will make qemu maintenance cheaper. So my preferred variant > is Even for Linux the rules aren't 100% black or white. There have been cases where small breakage are introduced, for example 4.12 will break the BLKDISCARDZEROES ioctl. We shouldn't treat things are black or white here too. "-usbdevice" makes sense to deprecate because it brings together a complicated parsing mechanism, though perhaps we could keep it for simple devices such as keyboard, mouse, tablet where it's pretty surely in use in the wild. "-drive cyls=..." also makes sense to deprecate because it is a very obscure functionality. "-drive serial=..." would be nice to deprecate, but I think it's already less clear that it's not in use in the wild. Probably it's still on the side of wanting to eventually remove it. "-net" is more complicated still. It's almost surely in use in the wild, but then probably the users are fairly advanced and (with the provision that documentation should be updated) I guess we could eventually get there. But I really, really see no point in removing --enable-kvm. It costs perhaps 10 lines of code that has pretty much no ramifications elsewhere in the code. If anything I'd expect "-machine accel" to disappear before, if ever (in favor of multiple "-accel" options, e.g. "-machine accel=kvm:tcg" can become "-accel kvm -accel tcg". Thanks, Paolo