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 96D16C433FE for ; Thu, 24 Feb 2022 20:46:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234258AbiBXUqj (ORCPT ); Thu, 24 Feb 2022 15:46:39 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42820 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233546AbiBXUqi (ORCPT ); Thu, 24 Feb 2022 15:46:38 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id C02D92763CB for ; Thu, 24 Feb 2022 12:46:07 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1645735566; 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=1xJkiVuDqLpP0r8DT6X5v+8nfBw19AQQbdmtTvgjsys=; b=TkAu5iVeDy0SFrjqBoy7TEJPi0N8d02csvVciRAdCcbCGwxOsevQlTz8Gom+LkN6iSVpZ2 s4zGBdY/NgfdTSoucK+4Z2Oj8SiVHpwO/1tXQIm4qClAF+7/PzR4+7Ak/EJk7XbcL4Ab/0 lJb0CYZ2HbM6HjjOBgEP0GAmIC6Z4Fc= Received: from mail-oi1-f199.google.com (mail-oi1-f199.google.com [209.85.167.199]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-630-qM8-iuv3NfaD_rRaYfzlew-1; Thu, 24 Feb 2022 15:46:05 -0500 X-MC-Unique: qM8-iuv3NfaD_rRaYfzlew-1 Received: by mail-oi1-f199.google.com with SMTP id s83-20020acaa956000000b002d41cfd2926so1933666oie.0 for ; Thu, 24 Feb 2022 12:46:05 -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:organization:mime-version:content-transfer-encoding; bh=1xJkiVuDqLpP0r8DT6X5v+8nfBw19AQQbdmtTvgjsys=; b=fDPKspfoRekQdyRh3TbbYp5dzpMuyM9vBvMNFpVuafvdAGF55BoFshxhyQ07H3FtCk 413Q+//y1WpSkYNDm0deGASL13o133LHJ5qVhNeuHnUxjUwptGPt95St6/zXGH8LmTtC 5v2NUevD+BEXxS2pnvg69x8mUCL+A4SSmp9EKgGhOVm7YdF8sUSOi5AsVKnuKnNYhpve VIlI5bHcGzAoRapUtp/ctWwaWU9S/zhvtw3ISGRGbyIusF8OtAfsUfnI+k+zFQobOFpG 37VkiWB6zm/oid5OgWzD6z7lOf7PGRfuUSn6WJqCPMmUqmrGXpEVJ94wPVwlDQBnZRe1 TeCQ== X-Gm-Message-State: AOAM5333l7ie/YeLHV1R5eGz0FhZB880EIMUZggv/cLGmjS2kM0Tsvc+ 7YX4+QYl4CQBa/3qaMBHgN9xe+xkoj3fpKHggOZzzHB9kMKOZQ+Yl5djisNBdX51N1+Q1TDU7GT eSclIR/IyN7JvTqeb X-Received: by 2002:a05:6870:a8ab:b0:d2:cd36:7859 with SMTP id eb43-20020a056870a8ab00b000d2cd367859mr6833982oab.83.1645735564909; Thu, 24 Feb 2022 12:46:04 -0800 (PST) X-Google-Smtp-Source: ABdhPJzz4xGGAZJSkc7LhAo0lyQZngfUJtqj1zh+GjitSeyjotMwtIhB98xlzX/VXd3Nwyom9gJpFQ== X-Received: by 2002:a05:6870:a8ab:b0:d2:cd36:7859 with SMTP id eb43-20020a056870a8ab00b000d2cd367859mr6833976oab.83.1645735564657; Thu, 24 Feb 2022 12:46:04 -0800 (PST) Received: from redhat.com ([38.15.36.239]) by smtp.gmail.com with ESMTPSA id g12-20020a056870340c00b000d17b798ba9sm357988oah.34.2022.02.24.12.46.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 24 Feb 2022 12:46:03 -0800 (PST) Date: Thu, 24 Feb 2022 13:46:02 -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, ashok.raj@intel.com, kevin.tian@intel.com, shameerali.kolothum.thodi@huawei.com Subject: Re: [PATCH V9 mlx5-next 10/15] vfio: Extend the device migration protocol with RUNNING_P2P Message-ID: <20220224134602.74c250d0.alex.williamson@redhat.com> In-Reply-To: <87czjc6w9k.fsf@redhat.com> References: <20220224142024.147653-1-yishaih@nvidia.com> <20220224142024.147653-11-yishaih@nvidia.com> <87fso870k8.fsf@redhat.com> <20220224083042.3f5ad059.alex.williamson@redhat.com> <20220224161330.GA19295@nvidia.com> <20220224093542.3730bb24.alex.williamson@redhat.com> <87czjc6w9k.fsf@redhat.com> Organization: Red Hat MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, 24 Feb 2022 17:53:59 +0100 Cornelia Huck wrote: > On Thu, Feb 24 2022, Alex Williamson wrote: > > Chatting with Connie offline, I think the clarification that might help > > is something alone the lines that the combination of bits must support > > migration, which currently requires the STOP_COPY and RESUMING states. > > The VFIO_MIGRATION_P2P flag alone does not provide these states. The > > only flag in the current specification to provide these states is > > VFIO_MIGRATION_STOP_COPY. I don't think we want to preclude that some > > future flag might provide variants of STOP_COPY and RESUMING, so it's > > not so much that VFIO_MIGRATION_STOP_COPY is mandatory, but it is > > currently the only flag which provides the base degree of migration > > support. > > Indeed. > > > > > How or if that translates to an actual documentation update, I'm not > > sure. As it stands, we're not speculating about future support, we're > > only stating these two combinations are valid. Future combinations may > > or may not include VFIO_MIGRATION_STOP_COPY. As the existing proposed > > comment indicates, other combinations are TBD. Connie? Thanks, > > > > Alex > > Hm... "a flag indicating support for a migration state machine such as > VFIO_MIGRATION_STOP_COPY is mandatory"? TBH, I'm not sure this makes a substantive improvement. We don't know what those new flag bits will be used for, including which bit or bits will combine to indicate a valid state machine. Userspace written to this spec needs to support STOP_COPY and optionally P2P as we're stating. Nothing really compels us to speculate general rules for unknown future bit combinations. Thanks, Alex