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=-3.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,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 D0DC3C433E0 for ; Sun, 7 Feb 2021 22:03:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 98EFB64E3E for ; Sun, 7 Feb 2021 22:03:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229621AbhBGWDX (ORCPT ); Sun, 7 Feb 2021 17:03:23 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57616 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229570AbhBGWDS (ORCPT ); Sun, 7 Feb 2021 17:03:18 -0500 Received: from mail-pl1-x62b.google.com (mail-pl1-x62b.google.com [IPv6:2607:f8b0:4864:20::62b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7C2F2C06174A for ; Sun, 7 Feb 2021 14:02:38 -0800 (PST) Received: by mail-pl1-x62b.google.com with SMTP id j11so6772051plt.11 for ; Sun, 07 Feb 2021 14:02:38 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amacapital-net.20150623.gappssmtp.com; s=20150623; h=content-transfer-encoding:from:mime-version:subject:date:message-id :references:cc:in-reply-to:to; bh=rF9rOEV9Q8WVIOH0rqIWO7EqANQSyBnp1ft+vyl9KF0=; b=QANXs0Ex159+byJKUEaE28kl3Xh1NJ9WQlAArBMiqR/LE0uHG9IpHhfqWrVmJbho7R zP1u0EqWhELbEmtTGccuSGqB1fhJqbp8L6ZAFLx9BsWQEpn7+9fUeq7ZlknoiHHfRYsV yCiSNhT/oz/MSrVIf+6C3avuFCznOmT2MIzTiHTudXkJ3md/uaNKYTp7OcY+zyFWUdx3 t2hI93ykFPrRg/ziGbbX6FfZAddsJEzERu6Jadvk5KI3v/9ZrpWsV/zrUDO5Y59dlxde zHUljpHpBinHt9TpnJyq7p6CZXtVOCBYq6uXD8Si3ujOPNxK8fpJ1Q0naopg0iRuSxBm +jGg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:content-transfer-encoding:from:mime-version :subject:date:message-id:references:cc:in-reply-to:to; bh=rF9rOEV9Q8WVIOH0rqIWO7EqANQSyBnp1ft+vyl9KF0=; b=akbvt0hbjL9kUaIpO2SC+BwU6l8sXHKim2SUUhB7zGidigLVpI+4t3mPEOGJHIUn8A 2vZz9yC2Nfe6t/heIy2LKeWChxNAi9BCc9UVIzcgrhRJsuCE3GTqeNLWlCd+NJAj7sNI BDIu34PKJ11W7RWBb2NgGTbkEZT6TGKCJnhJvcuwoDNPYi14Klj+1GOmX2snwVe+fpa3 1Pwsj5rYatJDybckF6puI3DbgTEBwjdeH8hfXpIw8bY9/7eEJrQgRdzMogj84YISrN4s +LzHdRjAHme4qGv0ZupXx41mo13Kw+Vfw82kY6W1Wpg2yzkDx/RiyOP7euszH/Q5AflE aSnw== X-Gm-Message-State: AOAM532YH1fc//rU9uYWOUOv4E1rhVflSyrdRhOwQ2j8vAG3CHn80te6 TZU8fIMU6RDZTnoXqU++9Y4meA== X-Google-Smtp-Source: ABdhPJzNR1bzv/JQhWJTt0CBbMKbJVt9xR9k8FE58XkDiaugfM9e0sPAPw9t+dZ9eAqufWWfnMqn+g== X-Received: by 2002:a17:90a:184:: with SMTP id 4mr13919868pjc.87.1612735358046; Sun, 07 Feb 2021 14:02:38 -0800 (PST) Received: from ?IPv6:2601:646:c200:1ef2:8e8:e217:43e7:e032? ([2601:646:c200:1ef2:8e8:e217:43e7:e032]) by smtp.gmail.com with ESMTPSA id i25sm16435713pgb.33.2021.02.07.14.02.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 07 Feb 2021 14:02:37 -0800 (PST) Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable From: Andy Lutomirski Mime-Version: 1.0 (1.0) Subject: Re: [RFC PATCH v3 1/2] mempinfd: Add new syscall to provide memory pin Date: Sun, 7 Feb 2021 14:02:36 -0800 Message-Id: References: <1612685884-19514-2-git-send-email-wangzhou1@hisilicon.com> Cc: linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-api@vger.kernel.org, Andrew Morton , Alexander Viro , gregkh@linuxfoundation.org, song.bao.hua@hisilicon.com, jgg@ziepe.ca, kevin.tian@intel.com, jean-philippe@linaro.org, eric.auger@redhat.com, liguozhu@hisilicon.com, zhangfei.gao@linaro.org, Sihang Chen In-Reply-To: <1612685884-19514-2-git-send-email-wangzhou1@hisilicon.com> To: Zhou Wang X-Mailer: iPhone Mail (18D52) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On Feb 7, 2021, at 12:31 AM, Zhou Wang wrote: >=20 > =EF=BB=BFSVA(share virtual address) offers a way for device to share proce= ss virtual > address space safely, which makes more convenient for user space device > driver coding. However, IO page faults may happen when doing DMA > operations. As the latency of IO page fault is relatively big, DMA > performance will be affected severely when there are IO page faults. > =46rom a long term view, DMA performance will be not stable. >=20 > In high-performance I/O cases, accelerators might want to perform > I/O on a memory without IO page faults which can result in dramatically > increased latency. Current memory related APIs could not achieve this > requirement, e.g. mlock can only avoid memory to swap to backup device, > page migration can still trigger IO page fault. >=20 > Various drivers working under traditional non-SVA mode are using > their own specific ioctl to do pin. Such ioctl can be seen in v4l2, > gpu, infiniband, media, vfio, etc. Drivers are usually doing dma > mapping while doing pin. >=20 > But, in SVA mode, pin could be a common need which isn't necessarily > bound with any drivers, and neither is dma mapping needed by drivers > since devices are using the virtual address of CPU. Thus, It is better > to introduce a new common syscall for it. >=20 > This patch leverages the design of userfaultfd and adds mempinfd for pin > to avoid messing up mm_struct. A fd will be got by mempinfd, then user > space can do pin/unpin pages by ioctls of this fd, all pinned pages under > one file will be unpinned in file release process. Like pin page cases in > other places, can_do_mlock is used to check permission and input > parameters. Can you document what the syscall does? Userfaultfd is an fd because one program controls another. Is mempinfd like= this?= 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=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 053C7C433DB for ; Sun, 7 Feb 2021 22:30:37 +0000 (UTC) Received: from silver.osuosl.org (smtp3.osuosl.org [140.211.166.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6C3BE64E2E for ; Sun, 7 Feb 2021 22:30:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6C3BE64E2E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=amacapital.net Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=iommu-bounces@lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by silver.osuosl.org (Postfix) with ESMTP id 20CD620387; Sun, 7 Feb 2021 22:30:36 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from silver.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Tk8udhQLDQSn; Sun, 7 Feb 2021 22:30:35 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [140.211.9.56]) by silver.osuosl.org (Postfix) with ESMTP id 38AA42001E; Sun, 7 Feb 2021 22:30:35 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 1D068C0174; Sun, 7 Feb 2021 22:30:35 +0000 (UTC) Received: from hemlock.osuosl.org (smtp2.osuosl.org [140.211.166.133]) by lists.linuxfoundation.org (Postfix) with ESMTP id F2B80C013A for ; Sun, 7 Feb 2021 22:30:32 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by hemlock.osuosl.org (Postfix) with ESMTP id D973586864 for ; Sun, 7 Feb 2021 22:30:32 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from hemlock.osuosl.org ([127.0.0.1]) by localhost (.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id cIcZO1OydmAY for ; Sun, 7 Feb 2021 22:30:32 +0000 (UTC) X-Greylist: delayed 00:19:45 by SQLgrey-1.7.6 Received: from mail-oi1-f178.google.com (mail-oi1-f178.google.com [209.85.167.178]) by hemlock.osuosl.org (Postfix) with ESMTPS id E90C48667B for ; Sun, 7 Feb 2021 22:30:31 +0000 (UTC) Received: by mail-oi1-f178.google.com with SMTP id v193so8356742oie.8 for ; Sun, 07 Feb 2021 14:30:31 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amacapital-net.20150623.gappssmtp.com; s=20150623; h=content-transfer-encoding:from:mime-version:subject:date:message-id :references:cc:in-reply-to:to; bh=rF9rOEV9Q8WVIOH0rqIWO7EqANQSyBnp1ft+vyl9KF0=; b=QANXs0Ex159+byJKUEaE28kl3Xh1NJ9WQlAArBMiqR/LE0uHG9IpHhfqWrVmJbho7R zP1u0EqWhELbEmtTGccuSGqB1fhJqbp8L6ZAFLx9BsWQEpn7+9fUeq7ZlknoiHHfRYsV yCiSNhT/oz/MSrVIf+6C3avuFCznOmT2MIzTiHTudXkJ3md/uaNKYTp7OcY+zyFWUdx3 t2hI93ykFPrRg/ziGbbX6FfZAddsJEzERu6Jadvk5KI3v/9ZrpWsV/zrUDO5Y59dlxde zHUljpHpBinHt9TpnJyq7p6CZXtVOCBYq6uXD8Si3ujOPNxK8fpJ1Q0naopg0iRuSxBm +jGg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:content-transfer-encoding:from:mime-version :subject:date:message-id:references:cc:in-reply-to:to; bh=rF9rOEV9Q8WVIOH0rqIWO7EqANQSyBnp1ft+vyl9KF0=; b=NGtcV3e3N30kykch2YjJLwmaUTHbR5T6bOooIYikKh9nSKeopH6lpE5jNMquQgzKRO sMW5gVwU/J3cDh2Aul9MoxqRJvOqSpNlRpopNzIhYEyLDZudD8G/qaZABPryggwwFxkL M5JUebVhmNXLua88bPhs0ylyxMZPYwtVSKq2fZsT8JGXJmEL127DMDfC1AkEoV/rb9zr LleMnN6V+sNVxRAxfkGAx9flVgXYCvopFAeK72E3WrH3PvjoH+ZWjmRZC3ulau1q3vgT y60Kk6KOmQecsB7MsMlGqHqOK2PtDKXQU4VNsdedZHRe1WwzOfctBozTSj8Ag/UTuDXT TKeQ== X-Gm-Message-State: AOAM530XeB57jIx5syPDbHtOCeucEAaM6vhDoQqdZ8+EiyqIdJLfADGP kN+RDJBEh1+CndHJbnM18HLUQRhuv7PrzS+T X-Google-Smtp-Source: ABdhPJzNR1bzv/JQhWJTt0CBbMKbJVt9xR9k8FE58XkDiaugfM9e0sPAPw9t+dZ9eAqufWWfnMqn+g== X-Received: by 2002:a17:90a:184:: with SMTP id 4mr13919868pjc.87.1612735358046; Sun, 07 Feb 2021 14:02:38 -0800 (PST) Received: from ?IPv6:2601:646:c200:1ef2:8e8:e217:43e7:e032? 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([2601:646:c200:1ef2:8e8:e217:43e7:e032]) by smtp.gmail.com with ESMTPSA id i25sm16435713pgb.33.2021.02.07.14.02.37 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sun, 07 Feb 2021 14:02:37 -0800 (PST) From: Andy Lutomirski Mime-Version: 1.0 (1.0) Subject: Re: [RFC PATCH v3 1/2] mempinfd: Add new syscall to provide memory pin Date: Sun, 7 Feb 2021 14:02:36 -0800 Message-Id: References: <1612685884-19514-2-git-send-email-wangzhou1@hisilicon.com> In-Reply-To: <1612685884-19514-2-git-send-email-wangzhou1@hisilicon.com> To: Zhou Wang X-Mailer: iPhone Mail (18D52) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210207_170242_209712_D54FE376 X-CRM114-Status: GOOD ( 16.32 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: song.bao.hua@hisilicon.com, jean-philippe@linaro.org, kevin.tian@intel.com, Sihang Chen , jgg@ziepe.ca, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Alexander Viro , eric.auger@redhat.com, gregkh@linuxfoundation.org, zhangfei.gao@linaro.org, Andrew Morton , liguozhu@hisilicon.com, linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Cgo+IE9uIEZlYiA3LCAyMDIxLCBhdCAxMjozMSBBTSwgWmhvdSBXYW5nIDx3YW5nemhvdTFAaGlz aWxpY29uLmNvbT4gd3JvdGU6Cj4gCj4g77u/U1ZBKHNoYXJlIHZpcnR1YWwgYWRkcmVzcykgb2Zm ZXJzIGEgd2F5IGZvciBkZXZpY2UgdG8gc2hhcmUgcHJvY2VzcyB2aXJ0dWFsCj4gYWRkcmVzcyBz cGFjZSBzYWZlbHksIHdoaWNoIG1ha2VzIG1vcmUgY29udmVuaWVudCBmb3IgdXNlciBzcGFjZSBk ZXZpY2UKPiBkcml2ZXIgY29kaW5nLiBIb3dldmVyLCBJTyBwYWdlIGZhdWx0cyBtYXkgaGFwcGVu IHdoZW4gZG9pbmcgRE1BCj4gb3BlcmF0aW9ucy4gQXMgdGhlIGxhdGVuY3kgb2YgSU8gcGFnZSBm YXVsdCBpcyByZWxhdGl2ZWx5IGJpZywgRE1BCj4gcGVyZm9ybWFuY2Ugd2lsbCBiZSBhZmZlY3Rl ZCBzZXZlcmVseSB3aGVuIHRoZXJlIGFyZSBJTyBwYWdlIGZhdWx0cy4KPiBGcm9tIGEgbG9uZyB0 ZXJtIHZpZXcsIERNQSBwZXJmb3JtYW5jZSB3aWxsIGJlIG5vdCBzdGFibGUuCj4gCj4gSW4gaGln aC1wZXJmb3JtYW5jZSBJL08gY2FzZXMsIGFjY2VsZXJhdG9ycyBtaWdodCB3YW50IHRvIHBlcmZv cm0KPiBJL08gb24gYSBtZW1vcnkgd2l0aG91dCBJTyBwYWdlIGZhdWx0cyB3aGljaCBjYW4gcmVz dWx0IGluIGRyYW1hdGljYWxseQo+IGluY3JlYXNlZCBsYXRlbmN5LiBDdXJyZW50IG1lbW9yeSBy ZWxhdGVkIEFQSXMgY291bGQgbm90IGFjaGlldmUgdGhpcwo+IHJlcXVpcmVtZW50LCBlLmcuIG1s b2NrIGNhbiBvbmx5IGF2b2lkIG1lbW9yeSB0byBzd2FwIHRvIGJhY2t1cCBkZXZpY2UsCj4gcGFn ZSBtaWdyYXRpb24gY2FuIHN0aWxsIHRyaWdnZXIgSU8gcGFnZSBmYXVsdC4KPiAKPiBWYXJpb3Vz IGRyaXZlcnMgd29ya2luZyB1bmRlciB0cmFkaXRpb25hbCBub24tU1ZBIG1vZGUgYXJlIHVzaW5n Cj4gdGhlaXIgb3duIHNwZWNpZmljIGlvY3RsIHRvIGRvIHBpbi4gU3VjaCBpb2N0bCBjYW4gYmUg c2VlbiBpbiB2NGwyLAo+IGdwdSwgaW5maW5pYmFuZCwgbWVkaWEsIHZmaW8sIGV0Yy4gRHJpdmVy cyBhcmUgdXN1YWxseSBkb2luZyBkbWEKPiBtYXBwaW5nIHdoaWxlIGRvaW5nIHBpbi4KPiAKPiBC dXQsIGluIFNWQSBtb2RlLCBwaW4gY291bGQgYmUgYSBjb21tb24gbmVlZCB3aGljaCBpc24ndCBu ZWNlc3NhcmlseQo+IGJvdW5kIHdpdGggYW55IGRyaXZlcnMsIGFuZCBuZWl0aGVyIGlzIGRtYSBt YXBwaW5nIG5lZWRlZCBieSBkcml2ZXJzCj4gc2luY2UgZGV2aWNlcyBhcmUgdXNpbmcgdGhlIHZp cnR1YWwgYWRkcmVzcyBvZiBDUFUuIFRodXMsIEl0IGlzIGJldHRlcgo+IHRvIGludHJvZHVjZSBh IG5ldyBjb21tb24gc3lzY2FsbCBmb3IgaXQuCj4gCj4gVGhpcyBwYXRjaCBsZXZlcmFnZXMgdGhl IGRlc2lnbiBvZiB1c2VyZmF1bHRmZCBhbmQgYWRkcyBtZW1waW5mZCBmb3IgcGluCj4gdG8gYXZv aWQgbWVzc2luZyB1cCBtbV9zdHJ1Y3QuIEEgZmQgd2lsbCBiZSBnb3QgYnkgbWVtcGluZmQsIHRo ZW4gdXNlcgo+IHNwYWNlIGNhbiBkbyBwaW4vdW5waW4gcGFnZXMgYnkgaW9jdGxzIG9mIHRoaXMg ZmQsIGFsbCBwaW5uZWQgcGFnZXMgdW5kZXIKPiBvbmUgZmlsZSB3aWxsIGJlIHVucGlubmVkIGlu IGZpbGUgcmVsZWFzZSBwcm9jZXNzLiBMaWtlIHBpbiBwYWdlIGNhc2VzIGluCj4gb3RoZXIgcGxh Y2VzLCBjYW5fZG9fbWxvY2sgaXMgdXNlZCB0byBjaGVjayBwZXJtaXNzaW9uIGFuZCBpbnB1dAo+ IHBhcmFtZXRlcnMuCgoKQ2FuIHlvdSBkb2N1bWVudCB3aGF0IHRoZSBzeXNjYWxsIGRvZXM/CgpV c2VyZmF1bHRmZCBpcyBhbiBmZCBiZWNhdXNlIG9uZSBwcm9ncmFtIGNvbnRyb2xzIGFub3RoZXIu ICBJcyBtZW1waW5mZCBsaWtlIHRoaXM/Cl9fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fX19fX19fCmxpbnV4LWFybS1rZXJuZWwgbWFpbGluZyBsaXN0CmxpbnV4LWFybS1r ZXJuZWxAbGlzdHMuaW5mcmFkZWFkLm9yZwpodHRwOi8vbGlzdHMuaW5mcmFkZWFkLm9yZy9tYWls bWFuL2xpc3RpbmZvL2xpbnV4LWFybS1rZXJuZWwK