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 B137DC433FE for ; Tue, 1 Feb 2022 23:01:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242525AbiBAXBL (ORCPT ); Tue, 1 Feb 2022 18:01:11 -0500 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:42107 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242497AbiBAXBL (ORCPT ); Tue, 1 Feb 2022 18:01:11 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1643756470; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ZZQsFy9xaSL/C+8tHxnl069hXf8XB97MOyjVaLm6KWA=; b=gPL4po6fTkOJxZ3jS15cGUu9Hk4q4r600itP89dn9uTHPjB3reWGyPK9Nv3NSjGTak+ciJ bCocr7JzzMNLljAZnH/TsI2y7nXpgRyw8O0Jj/SqFxjk7UoVPDh+63/z03cEbLg2E+8Sr0 ZPwrUK+Y8pA2PRi98IohowQrzW8UNIw= Received: from mail-oi1-f198.google.com (mail-oi1-f198.google.com [209.85.167.198]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-228-AwJ6rlirOBKOgDbeM-1FTw-1; Tue, 01 Feb 2022 18:01:09 -0500 X-MC-Unique: AwJ6rlirOBKOgDbeM-1FTw-1 Received: by mail-oi1-f198.google.com with SMTP id ay31-20020a056808301f00b002d06e828c00so2789769oib.2 for ; Tue, 01 Feb 2022 15:01:09 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=ZZQsFy9xaSL/C+8tHxnl069hXf8XB97MOyjVaLm6KWA=; b=prANdQ2n/cL7tgpgZazzIzM4lbwG6Hw3dZCb/uB34zLIEqGAOJT3Sz6WR2L+RnoG4m 6viUt3Vt7WZNhAqIEUfw7XfSt8X5kkBaG8ATYxpu02BWz5BN/KZe2xBdtan449I5/B3V 6WeK7XepubYgWrL2TAWxFPAweHdGi6QMKjg+b1T6RTbr4fps7uEdKSkLMKwu6xvVCHBt KF0OPwLSGtP2D//8nUC9z89iDMCBcPFpK/UneYIg4Uj0r+Q8z7IsaMe93g9GKpjRQsTA Idu8n2ekCZhVfp1T7NQ108nYuzk5PgDVD6Fr6dLb+Rt2GYcn4wOTW7E3IaE3ZiK+PCxp Bu/Q== X-Gm-Message-State: AOAM531zSEEXcAhEazCap+CfWIqsphwJdCJoIeBLperCukXnlW6DrNGl Unl2tRFccTOorpNsLXLsFWEGlnvYX8sbEfnofXmUY9fxXwU+GoBO/etosU7+zAzkvbrWDcHrne0 0DEnxZWREPul0SqOdhZxJ X-Received: by 2002:a05:6808:20a7:: with SMTP id s39mr2718321oiw.306.1643756468634; Tue, 01 Feb 2022 15:01:08 -0800 (PST) X-Google-Smtp-Source: ABdhPJxcB506OEAhqOJI745n4wG5GysVpVVMM9JD8hrzIrz8J+sFhUk3i/Fjf/mS8Hij0DFXWZZ5bQ== X-Received: by 2002:a05:6808:20a7:: with SMTP id s39mr2718298oiw.306.1643756468405; Tue, 01 Feb 2022 15:01:08 -0800 (PST) Received: from redhat.com ([38.15.36.239]) by smtp.gmail.com with ESMTPSA id bf15sm1581295oib.32.2022.02.01.15.01.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Feb 2022 15:01:08 -0800 (PST) Date: Tue, 1 Feb 2022 16:01:06 -0700 From: Alex Williamson To: Cornelia Huck Cc: Jason Gunthorpe , Yishai Hadas , bhelgaas@google.com, saeedm@nvidia.com, linux-pci@vger.kernel.org, kvm@vger.kernel.org, netdev@vger.kernel.org, kuba@kernel.org, leonro@nvidia.com, kwankhede@nvidia.com, mgurtovoy@nvidia.com, maorg@nvidia.com Subject: Re: [PATCH V6 mlx5-next 10/15] vfio: Remove migration protocol v1 Message-ID: <20220201160106.0760bfea.alex.williamson@redhat.com> In-Reply-To: <87sft2yd50.fsf@redhat.com> References: <20220130160826.32449-1-yishaih@nvidia.com> <20220130160826.32449-11-yishaih@nvidia.com> <874k5izv8m.fsf@redhat.com> <20220201121325.GB1786498@nvidia.com> <87sft2yd50.fsf@redhat.com> X-Mailer: Claws Mail 3.18.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Tue, 01 Feb 2022 13:39:23 +0100 Cornelia Huck wrote: > On Tue, Feb 01 2022, Jason Gunthorpe wrote: > > > On Tue, Feb 01, 2022 at 12:23:05PM +0100, Cornelia Huck wrote: > >> On Sun, Jan 30 2022, Yishai Hadas wrote: > >> > >> > From: Jason Gunthorpe > >> > > >> > v1 was never implemented and is replaced by v2. > >> > > >> > The old uAPI definitions are removed from the header file. As per Linus's > >> > past remarks we do not have a hard requirement to retain compilation > >> > compatibility in uapi headers and qemu is already following Linus's > >> > preferred model of copying the kernel headers. > >> > >> If we are all in agreement that we will replace v1 with v2 (and I think > >> we are), we probably should remove the x-enable-migration stuff in QEMU > >> sooner rather than later, to avoid leaving a trap for the next > >> unsuspecting person trying to update the headers. > > > > Once we have agreement on the kernel patch we plan to send a QEMU > > patch making it support the v2 interface and the migration > > non-experimental. We are also working to fixing the error paths, at > > least least within the limitations of the current qemu design. > > I'd argue that just ripping out the old interface first would be easier, > as it does not require us to synchronize with a headers sync (and does > not require to synchronize a headers sync with ripping it out...) > > > The v1 support should remain in old releases as it is being used in > > the field "experimentally". > > Of course; it would be hard to rip it out retroactively :) > > But it should really be gone in QEMU 7.0. > > Considering adding the v2 uapi, we might get unlucky: The Linux 5.18 > merge window will likely be in mid-late March (and we cannot run a > headers sync before the patches hit Linus' tree), while QEMU 7.0 will > likely enter freeze in mid-late March as well. So there's a non-zero > chance that the new uapi will need to be deferred to 7.1. Agreed that v1 migration TYPE/SUBTYPE should live in infamy as reserved, but I'm not sure why we need to make the rest of it a big complicated problem. On one hand, leaving stubs for the necessary structure and macros until QEMU gets updated doesn't seem so terrible. Nor actually does letting the next QEMU header update cause build breakages, which would probably frustrate the person submitting that update, but it's not like QEMU hasn't done selective header updates in the past. The former is probably the more friendly approach if we don't outrage someone in the kernel community in the meantime. Thanks, Alex