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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 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 39305C432C1 for ; Wed, 25 Sep 2019 07:45:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 0FAFC2054F for ; Wed, 25 Sep 2019 07:45:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2442413AbfIYHpV (ORCPT ); Wed, 25 Sep 2019 03:45:21 -0400 Received: from mx1.redhat.com ([209.132.183.28]:47144 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2394933AbfIYHpV (ORCPT ); Wed, 25 Sep 2019 03:45:21 -0400 Received: from mail-pl1-f199.google.com (mail-pl1-f199.google.com [209.85.214.199]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 7553363704 for ; Wed, 25 Sep 2019 07:45:20 +0000 (UTC) Received: by mail-pl1-f199.google.com with SMTP id b23so2841495pls.8 for ; Wed, 25 Sep 2019 00:45:20 -0700 (PDT) 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:user-agent; bh=lGlfVebe14dEyAwlNX/fOfUXOsimPZPypK8xTf2N4Zk=; b=HuSCjVHkESHfrujmIfLVWAVUF6uAEmmwV0tvzzuU5gbrbHKg4YEEpu+gTmMZ5ztzWD BoC7S5He8kF7o50A5C+nDFpr4tZpi26bzRg8XSqG+OOoK991k5waq5VnEvGsdH+0yyk0 1WnaJiNsvnup7/0S9FK1UovmVY1DfTdle4i1MBefvCd7zVrU+0s3BCFqoUy7AI/0HLwU QbQeHg6gyQy/iFKU3ojizQ7AZ/0pwAN8fS61180UPA/EEKIbCnpILCzPvtRGO2VyB3di Dl4M51v6i4GM0VM9rZthqQFpHEMC480zTVMfSSVYu0rEoSk566dIpLHjXcxer7487etV LoVQ== X-Gm-Message-State: APjAAAUch25UYXQvDWqFN/586VkdTMPGLtgNlwd/DxsVHKbQJ29ivoZY ucxdqbsCVdG+hohqt5UyqRQ4nBuL2x9mB5RCJTeF7lpRK/4OlfxKteUvFRIzg0vAAg9viG1b7ZZ jhxyAW1qA3v0+PAWRUXbT1GmB X-Received: by 2002:a17:902:7c94:: with SMTP id y20mr7255441pll.229.1569397519932; Wed, 25 Sep 2019 00:45:19 -0700 (PDT) X-Google-Smtp-Source: APXvYqwCHx/3JAR/6+/InK/am42O9UXzLwb84IAvlRe5LPMfo5VvBXJdpQbI+cKfEX19uVulZcYtcw== X-Received: by 2002:a17:902:7c94:: with SMTP id y20mr7255402pll.229.1569397519622; Wed, 25 Sep 2019 00:45:19 -0700 (PDT) Received: from xz-x1 ([209.132.188.80]) by smtp.gmail.com with ESMTPSA id p17sm5670841pfn.50.2019.09.25.00.45.14 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Sep 2019 00:45:18 -0700 (PDT) Date: Wed, 25 Sep 2019 15:45:07 +0800 From: Peter Xu To: "Tian, Kevin" Cc: Lu Baolu , "Raj, Ashok" , Jacob Pan , "kvm@vger.kernel.org" , "Kumar, Sanjay K" , "Sun, Yi Y" , "iommu@lists.linux-foundation.org" , "linux-kernel@vger.kernel.org" , Alex Williamson , David Woodhouse Subject: Re: [RFC PATCH 0/4] Use 1st-level for DMA remapping in guest Message-ID: <20190925074507.GP28074@xz-x1> References: <20190923122454.9888-1-baolu.lu@linux.intel.com> <20190923122715.53de79d0@jacob-builder> <20190923202552.GA21816@araj-mobl1.jf.intel.com> <20190925065640.GO28074@xz-x1> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.4 (2019-03-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Sep 25, 2019 at 07:21:51AM +0000, Tian, Kevin wrote: > > From: Peter Xu [mailto:peterx@redhat.com] > > Sent: Wednesday, September 25, 2019 2:57 PM > > > > On Wed, Sep 25, 2019 at 10:48:32AM +0800, Lu Baolu wrote: > > > Hi Kevin, > > > > > > On 9/24/19 3:00 PM, Tian, Kevin wrote: > > > > > > > '-----------' > > > > > > > '-----------' > > > > > > > > > > > > > > This patch series only aims to achieve the first goal, a.k.a using > > > > first goal? then what are other goals? I didn't spot such information. > > > > > > > > > > The overall goal is to use IOMMU nested mode to avoid shadow page > > table > > > and VMEXIT when map an gIOVA. This includes below 4 steps (maybe not > > > accurate, but you could get the point.) > > > > > > 1) GIOVA mappings over 1st-level page table; > > > 2) binding vIOMMU 1st level page table to the pIOMMU; > > > 3) using pIOMMU second level for GPA->HPA translation; > > > 4) enable nested (a.k.a. dual stage) translation in host. > > > > > > This patch set aims to achieve 1). > > > > Would it make sense to use 1st level even for bare-metal to replace > > the 2nd level? > > > > What I'm thinking is the DPDK apps - they have MMU page table already > > there for the huge pages, then if they can use 1st level as the > > default device page table then it even does not need to map, because > > it can simply bind the process root page table pointer to the 1st > > level page root pointer of the device contexts that it uses. > > > > Then you need bear with possible page faults from using CPU page > table, while most devices don't support it today. Right, I was just thinking aloud. After all neither do we have IOMMU hardware to support 1st level (or am I wrong?)... It's just that when the 1st level is ready it should sound doable because IIUC PRI should be always with the 1st level support no matter on IOMMU side or the device side? I'm actually not sure about whether my understanding here is correct... I thought the pasid binding previously was only for some vendor kernel drivers but not a general thing to userspace. I feel like that should be doable in the future once we've got some new syscall interface ready to deliver 1st level page table (e.g., via vfio?) then applications like DPDK seems to be able to use that too even directly via bare metal. Regards, -- Peter Xu