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 X-Spam-Level: X-Spam-Status: No, score=-0.9 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D1CEAC32771 for ; Mon, 20 Jan 2020 21:25:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 972FE217F4 for ; Mon, 20 Jan 2020 21:25:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="WHiMVwVc" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726935AbgATVZg (ORCPT ); Mon, 20 Jan 2020 16:25:36 -0500 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:24002 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726586AbgATVZg (ORCPT ); Mon, 20 Jan 2020 16:25:36 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1579555534; 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: in-reply-to:in-reply-to:references:references; bh=9l++3OuyTlK7LXp5Mq/OwpRSmGcumz9fcGOybYboMEQ=; b=WHiMVwVcmNRiQD9A/07hlrlU6QyJ1ae/VM9SN0q8sj/dosmZDJu9E2ItgDhAhqdnz10AGR NdyiOSLTmCtuYqsCoZFHopxfoy4F9UVrcR6t+XgCSn8fKIDD9u/Ulbss9xuk0K/RufEoTo /KnZq2sVZkeJj6rKc9QqJTji7DyY1uI= Received: from mail-qk1-f198.google.com (mail-qk1-f198.google.com [209.85.222.198]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-232-ULBj1PcgOv-FXjf7cWLojg-1; Mon, 20 Jan 2020 16:25:33 -0500 X-MC-Unique: ULBj1PcgOv-FXjf7cWLojg-1 Received: by mail-qk1-f198.google.com with SMTP id a73so538123qkg.5 for ; Mon, 20 Jan 2020 13:25:33 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=9l++3OuyTlK7LXp5Mq/OwpRSmGcumz9fcGOybYboMEQ=; b=bvQGLwJEAsZJYLXbcNx2TuHKFhx1kkhFSFVgZoG7k5/1lpWPg34n5UHAanwZ0apB6B RhwfSdDBJHHMuyjkte7P4PVGMhYwDwlRkuYXnk47v9YFrnfMiNWQByb6x2RQ7JMIdfT0 8m/3cohxziIxrZ9Shqig2FzLwOY8bI/Kmf8R6yk7RMtK8Ri6TCFEfgkvNTLL/fvmg5PI 9lmull+PPSiIXKykEJTJbKjqPJOYVihT4FZhoZsHYqY4K+hPpKKhMrbT5jpXGLtsXTZB inoCAAIeLoYsFajcgrVEQYHNk39joLH7sSmCpgzhGPvZ13HF+GUaWh2oam81B00OWPkl LGhw== X-Gm-Message-State: APjAAAXwwsw9J3+brbAyybYTC+bdfRYJIivKnTxaX7Xsq9ef63H91AqF q8RlChFwt+DA/jnmckfs6y1XSaax7dV5vHZ/NVXQSl+qoWluF11iTSOqkiDqmHy25rjMGLdp9/5 wgd4ERStyAwiehknhWYvZUT2h X-Received: by 2002:ac8:1196:: with SMTP id d22mr1407848qtj.344.1579555532892; Mon, 20 Jan 2020 13:25:32 -0800 (PST) X-Google-Smtp-Source: APXvYqywvPPeh7FgOr2FVgGg2WUbLkkvTqU5itT+MWratS+JkuLjho3cX5Dq8zUicH4JEtMdHkf1hA== X-Received: by 2002:ac8:1196:: with SMTP id d22mr1407821qtj.344.1579555532648; Mon, 20 Jan 2020 13:25:32 -0800 (PST) Received: from redhat.com (bzq-79-179-85-180.red.bezeqint.net. [79.179.85.180]) by smtp.gmail.com with ESMTPSA id f19sm16201765qkk.69.2020.01.20.13.25.25 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 20 Jan 2020 13:25:31 -0800 (PST) Date: Mon, 20 Jan 2020 16:25:23 -0500 From: "Michael S. Tsirkin" To: Shahaf Shuler Cc: Jason Gunthorpe , Jason Wang , Rob Miller , "linux-kernel@vger.kernel.org" , "kvm@vger.kernel.org" , "virtualization@lists.linux-foundation.org" , Netdev , "Bie, Tiwei" , "maxime.coquelin@redhat.com" , "Liang, Cunming" , "Wang, Zhihong" , "Wang, Xiao W" , "haotian.wang@sifive.com" , "Zhu, Lingshan" , "eperezma@redhat.com" , "lulu@redhat.com" , Parav Pandit , "Tian, Kevin" , "stefanha@redhat.com" , "rdunlap@infradead.org" , "hch@infradead.org" , Ariel Adam , "jakub.kicinski@netronome.com" , Jiri Pirko , "hanand@xilinx.com" , "mhabets@solarflare.com" Subject: Re: [PATCH 3/5] vDPA: introduce vDPA bus Message-ID: <20200120162449-mutt-send-email-mst@kernel.org> References: <20200116124231.20253-1-jasowang@redhat.com> <20200116124231.20253-4-jasowang@redhat.com> <20200117070324-mutt-send-email-mst@kernel.org> <239b042c-2d9e-0eec-a1ef-b03b7e2c5419@redhat.com> <20200120174933.GB3891@mellanox.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jan 20, 2020 at 08:51:43PM +0000, Shahaf Shuler wrote: > Monday, January 20, 2020 7:50 PM, Jason Gunthorpe: > > Subject: Re: [PATCH 3/5] vDPA: introduce vDPA bus > > > > On Mon, Jan 20, 2020 at 04:43:53PM +0800, Jason Wang wrote: > > > This is similar to the design of platform IOMMU part of vhost-vdpa. We > > > decide to send diffs to platform IOMMU there. If it's ok to do that in > > > driver, we can replace set_map with incremental API like map()/unmap(). > > > > > > Then driver need to maintain rbtree itself. > > > > I think we really need to see two modes, one where there is a fixed > > translation without dynamic vIOMMU driven changes and one that supports > > vIOMMU. > > > > There are different optimization goals in the drivers for these two > > configurations. > > +1. > It will be best to have one API for static config (i.e. mapping can be > set only before virtio device gets active), and one API for dynamic > changes that can be set after the virtio device is active. Frankly I don't see when we'd use the static one. Memory hotplug is enabled for most guests... > > > > > > If the first one, then I think memory hotplug is a heavy flow > > > > regardless. Do you think the extra cycles for the tree traverse will > > > > be visible in any way? > > > > > > I think if the driver can pause the DMA during the time for setting up > > > new mapping, it should be fine. > > > > This is very tricky for any driver if the mapping change hits the virtio rings. :( > > > > Even a IOMMU using driver is going to have problems with that.. > > > > Jason