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=-8.2 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,USER_AGENT_SANE_1 autolearn=ham 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 23F45C47083 for ; Wed, 2 Jun 2021 08:54:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0DCC2613D0 for ; Wed, 2 Jun 2021 08:54:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232918AbhFBI4W (ORCPT ); Wed, 2 Jun 2021 04:56:22 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:22323 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229959AbhFBI4R (ORCPT ); Wed, 2 Jun 2021 04:56:17 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1622624074; 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=TOI6E9j/kLUqqLzfWVG9w8giJlysUj5C+KWef8bCQ8I=; b=iey3U79HA+VvTZDpvn1WzZuVy5l3v5TtkaaFIzHe2il5HHOOGPHzbDXGtiQDNBsOFN19sO mNTCWKrpE+y6XmGPFu41oA/AWk/aqGo8VO6vkp0q+3NJdCwM6Iezl+7WPJ+YfRIsxQXClb E0mOrFzHtGAgKY6sPrOW8RlG6yeWu6k= Received: from mail-pj1-f70.google.com (mail-pj1-f70.google.com [209.85.216.70]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-587-crJ3WZQkN7OnZAcNfywdJg-1; Wed, 02 Jun 2021 04:54:33 -0400 X-MC-Unique: crJ3WZQkN7OnZAcNfywdJg-1 Received: by mail-pj1-f70.google.com with SMTP id o1-20020a17090a4201b029015c8f11f550so3021510pjg.5 for ; Wed, 02 Jun 2021 01:54:32 -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=TOI6E9j/kLUqqLzfWVG9w8giJlysUj5C+KWef8bCQ8I=; b=VLlT80TUVbTt/NNew7xDhDQneGDHwqaNAFMh2wREZy/DS5sBKcIGJiY7H10lzrCmiM yZ1/XXBYrI9kL8jCuzPXBi9mQKUrm3n7D/+oa1rrfdiDNZC68nwWMvnu0Rs2xN4vSanq bZ6y19M5hI7yU+scSh7sRm2rhDD1x1LOPFH8ylhldovvdZmwu8xHDFpFCCgrkAqMGV9i 9kueL5ThR4UgjK3DQgSca1o5PmSZylcWNIntomB1Gngu2KcTV9tN0qkhLgAb+RWfy06c 2NNZjfBknYxQjoDLmETgyO+9y4oi5c29ByH1FAmX/ddUum3wTrRdVRuYDcyJU9umMyZ5 GBMQ== X-Gm-Message-State: AOAM530L8RQ4dsEwrSR/JvDmacBZ7/fRJhVpEIyzx61peOWc2LvHf0DP DlDc/YgbP4N9u3e0CqZUKLj7aD1ilr4xgG8aTaBjGhkvhg1bCrE6OMFCon3TqfjnEebc1Rf1ukj NPrNdapdF9RFe X-Received: by 2002:a17:90a:7306:: with SMTP id m6mr4486585pjk.217.1622624072029; Wed, 02 Jun 2021 01:54:32 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzQ9jinHicYAMXd7FQEuh3El0Ofh9v6RECp7TK6Os2FVDpLb1bDFUCefzQjoGn2stvAL6/t8g== X-Received: by 2002:a17:90a:7306:: with SMTP id m6mr4486565pjk.217.1622624071836; Wed, 02 Jun 2021 01:54:31 -0700 (PDT) Received: from wangxiaodeMacBook-Air.local ([209.132.188.80]) by smtp.gmail.com with ESMTPSA id w2sm4060045pfc.126.2021.06.02.01.54.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 02 Jun 2021 01:54:31 -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: <20210531164118.265789ee@yiliu-dev> <78ee2638-1a03-fcc8-50a5-81040f677e69@redhat.com> <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> From: Jason Wang Message-ID: Date: Wed, 2 Jun 2021 16:54:26 +0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.10.2 MIME-Version: 1.0 In-Reply-To: <20210601173138.GM1002214@nvidia.com> Content-Type: text/plain; charset=gbk; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org ÔÚ 2021/6/2 ÉÏÎç1:31, Jason Gunthorpe дµÀ: > 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. And with the current proposal, (assuming there's a N:1 ioasid to ioasid). I wonder how select can work for the specific ioasid. Thanks > > A huge number of FDs for typical usages should be avoided. > > Jason >