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=-7.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,NICE_REPLY_A,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 B5F6FC47094 for ; Tue, 8 Jun 2021 01:10:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9199561263 for ; Tue, 8 Jun 2021 01:10:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231265AbhFHBMs (ORCPT ); Mon, 7 Jun 2021 21:12:48 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:57984 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230314AbhFHBMr (ORCPT ); Mon, 7 Jun 2021 21:12:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1623114654; 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=Ble1OdVWSdUFgnj3SJybSz6FbcPfrGdp/yR5UPi1dnM=; b=AGe7Fw91N1N6Q9oa+tcu78UcGYNg4ht+CpaAlYW6REyw25JrB4NW5BROsVqDwwDz/9IJOz yLyftKoO3r/Egxi1AP0jiqPYh7Y/1kQ4//ag0tQ2BFNXKn+Hq13IYaZD7Fi/IL3W1BNF+A UaCtiVFLanXtrmgMoPLhqrFYl8Cfe7E= Received: from mail-pf1-f200.google.com (mail-pf1-f200.google.com [209.85.210.200]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-488-OMORsP7hOCmLG_-Fssrn1A-1; Mon, 07 Jun 2021 21:10:53 -0400 X-MC-Unique: OMORsP7hOCmLG_-Fssrn1A-1 Received: by mail-pf1-f200.google.com with SMTP id k22-20020aa788d60000b02902ec984951ffso3898080pff.11 for ; Mon, 07 Jun 2021 18:10:53 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=Ble1OdVWSdUFgnj3SJybSz6FbcPfrGdp/yR5UPi1dnM=; b=HRnTnzorX+hrPnLKJqbpIEiMEzKoHLuCTHH4Kg4jMEBasnr49M9+kq0RDuGzEB5wsc tDnjgznQXR68hdxn2ALUuNRznMDLyrzCWhidvcg//2+uZbzBsx650/XisIbrlGHebNZD OI5S24+dSn53WNSKpgdTjVynndCheyIkxKk5F+FUpErMBnP/3Uvgs783pB0Dh2bWz0A0 cnG/Ggzhdq7/n9mn4kDkRZD0szYg/0oDH5pjqu7593LrNKfedSUT5WvPamXy0vCKdcqp Op6HG6NnKzr5U8I3QhiTXlfqk3I0fZLZL8slDr/sXTL/NfKJhLe7EoC7Vnfh9b/jd1I4 +/Xw== X-Gm-Message-State: AOAM530e+GIno5h5lLwGz6naYgx/ntW+g13N5F0aMJ7Yezza+Xbj9WRf Loyvm01oay8bddPsXe4nIc4ni/PiWI7Y2nvESSj3bG3cU/Ufy9gZg7DPzmSy66uvAz0LZlI95k7 1wUDMsK1ZdDNY X-Received: by 2002:a17:90b:318:: with SMTP id ay24mr23612461pjb.175.1623114652573; Mon, 07 Jun 2021 18:10:52 -0700 (PDT) X-Google-Smtp-Source: ABdhPJx253KrivISywGLROa5WGmZPzIUrrh3/ViJVkQze+aUvfxcfFXPOZCDpYA7zhgges937Rhj+Q== X-Received: by 2002:a17:90b:318:: with SMTP id ay24mr23612437pjb.175.1623114652306; Mon, 07 Jun 2021 18:10:52 -0700 (PDT) Received: from wangxiaodeMacBook-Air.local ([209.132.188.80]) by smtp.gmail.com with ESMTPSA id c5sm6947662pfn.144.2021.06.07.18.10.47 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 07 Jun 2021 18:10:51 -0700 (PDT) Subject: Re: [RFC] /dev/ioasid uAPI proposal To: Jason Gunthorpe Cc: "Tian, Kevin" , Lu Baolu , Liu Yi L , "kvm@vger.kernel.org" , Jonathan Corbet , "iommu@lists.linux-foundation.org" , LKML , "Alex Williamson (alex.williamson@redhat.com)\"\"" , David Woodhouse References: <20210601113152.6d09e47b@yiliu-dev> <164ee532-17b0-e180-81d3-12d49b82ac9f@redhat.com> <64898584-a482-e6ac-fd71-23549368c508@linux.intel.com> <429d9c2f-3597-eb29-7764-fad3ec9a934f@redhat.com> <05d7f790-870d-5551-1ced-86926a0aa1a6@redhat.com> <42a71462-1abc-0404-156c-60a7ee1ad333@redhat.com> <20210601173138.GM1002214@nvidia.com> <20210602172154.GC1002214@nvidia.com> From: Jason Wang Message-ID: Date: Tue, 8 Jun 2021 09:10:42 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.11.0 MIME-Version: 1.0 In-Reply-To: <20210602172154.GC1002214@nvidia.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org 在 2021/6/3 上午1:21, Jason Gunthorpe 写道: > On Wed, Jun 02, 2021 at 04:54:26PM +0800, Jason Wang wrote: >> 在 2021/6/2 上午1:31, Jason Gunthorpe 写道: >>> On Tue, Jun 01, 2021 at 04:47:15PM +0800, Jason Wang wrote: >>>> We can open up to ~0U file descriptors, I don't see why we need to restrict >>>> it in uAPI. >>> There are significant problems with such large file descriptor >>> tables. High FD numbers man things like select don't work at all >>> anymore and IIRC there are more complications. >> >> I don't see how much difference for IOASID and other type of fds. People can >> choose to use poll or epoll. > Not really, once one thing in an applicate uses a large number FDs the > entire application is effected. If any open() can return 'very big > number' then nothing in the process is allowed to ever use select. > > It is not a trivial thing to ask for > >> And with the current proposal, (assuming there's a N:1 ioasid to ioasid). I >> wonder how select can work for the specific ioasid. > pagefault events are one thing that comes to mind. Bundling them all > together into a single ring buffer is going to be necessary. Multifds > just complicate this too > > Jason Well, this sounds like a re-invention of io_uring which has already worked for multifds. Thanks