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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 64013C6FD1D for ; Thu, 23 Mar 2023 11:45:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231718AbjCWLpm (ORCPT ); Thu, 23 Mar 2023 07:45:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41690 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231681AbjCWLpj (ORCPT ); Thu, 23 Mar 2023 07:45:39 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9B1B11D907 for ; Thu, 23 Mar 2023 04:44:50 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1679571889; 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=BMD7H2kp0eSKoSxfq1PhoExu63Twb+QYc8ILXExIOt0=; b=R7dWtzTpD9n2TfgKI/ljFG79xAoZjHEiZfih/5Nz4fBDxChSGZg6lso0FW9ke8c9LLXA6L 60yE0xFbUT0UGgcFpLXD1JoE4jquUjf5h81cu1qLLrwQrWsx0HUWKLA0h7vayl+Qegjkls WGl8W9ZyXDtpEp8AFMEnbmSqXZefkvM= Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-596-hbP-rUTeNlOWXlSc7GrFXw-1; Thu, 23 Mar 2023 07:44:48 -0400 X-MC-Unique: hbP-rUTeNlOWXlSc7GrFXw-1 Received: by mail-ed1-f72.google.com with SMTP id t14-20020a056402240e00b004fb36e6d670so31647935eda.5 for ; Thu, 23 Mar 2023 04:44:48 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1679571887; h=in-reply-to:content-transfer-encoding:content-disposition :mime-version:references:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=BMD7H2kp0eSKoSxfq1PhoExu63Twb+QYc8ILXExIOt0=; b=ODwRUdFfC4a4H7gQ4zlrXADg5rYuJTWgp+HEOLM4k9caULuui9jsH4dfeCsXDnILew 2qOLja1hgPOS4Maj1M4QyWrB0sD8wtdgrZfSp+0NJ/9yJAbWwHDxyaFfvw7Se/p5flvW d1v1eEXFHGt8clGPcZbydo+L5p+qtehLfnPJPLsS7o0qHIEemRVVr9WJrQtLhtBpm5aE GIaeL5rGNS/12KaTGGkf/fuemn5NMFzTe8/8gzi9ydhRg2cvuBTiKhmWfwew9mNWz1w3 SysSQ1Gdq1b+lzI4Z3xEj/7LMxZNg+pdY7LlrCzcfeW+ywuch+yNUfkrWoxWCU6rKiIs bD4w== X-Gm-Message-State: AO0yUKUqrFUl8o0zs9WeOd8YtBh4imMIABuymp2uAfqj+zcKnfQOyAlb C8x9f3Jxd5ADWrrkMBJFo1W9L2n4v28ANFHRJa7oCewZn4mj9Ui0wgg6t3DhwTBVSYCMF/TOMIL cHuCAUR2FB7rJUOzImVsyF1qZ X-Received: by 2002:a05:6402:2920:b0:500:2cc6:36d5 with SMTP id ee32-20020a056402292000b005002cc636d5mr5727069edb.8.1679571887368; Thu, 23 Mar 2023 04:44:47 -0700 (PDT) X-Google-Smtp-Source: AK7set8uU0070bRsyBjQjpSi08yAtED4W63tVlm60HDGu5Op0XDHfVKzvp9t3BqE4omUQn4yYVC+6A== X-Received: by 2002:a05:6402:2920:b0:500:2cc6:36d5 with SMTP id ee32-20020a056402292000b005002cc636d5mr5727043edb.8.1679571887109; Thu, 23 Mar 2023 04:44:47 -0700 (PDT) Received: from redhat.com ([2.52.143.71]) by smtp.gmail.com with ESMTPSA id w3-20020a50c443000000b004ac54d4da22sm9165128edf.71.2023.03.23.04.44.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Mar 2023 04:44:46 -0700 (PDT) Date: Thu, 23 Mar 2023 07:44:43 -0400 From: "Michael S. Tsirkin" To: Stefano Garzarella Cc: Jason Wang , virtualization@lists.linux-foundation.org, kvm@vger.kernel.org, stefanha@redhat.com, linux-kernel@vger.kernel.org, eperezma@redhat.com, Andrey Zhadchenko , netdev@vger.kernel.org Subject: Re: [PATCH v3 8/8] vdpa_sim: add support for user VA Message-ID: <20230323074427-mutt-send-email-mst@kernel.org> References: <20230321154804.184577-1-sgarzare@redhat.com> <20230321154804.184577-4-sgarzare@redhat.com> <20230323095006.jvbbdjvkdvhzcehz@sgarzare-redhat> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20230323095006.jvbbdjvkdvhzcehz@sgarzare-redhat> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 23, 2023 at 10:50:06AM +0100, Stefano Garzarella wrote: > On Thu, Mar 23, 2023 at 11:42:07AM +0800, Jason Wang wrote: > > On Tue, Mar 21, 2023 at 11:48 PM Stefano Garzarella wrote: > > > > > > The new "use_va" module parameter (default: true) is used in > > > vdpa_alloc_device() to inform the vDPA framework that the device > > > supports VA. > > > > > > vringh is initialized to use VA only when "use_va" is true and the > > > user's mm has been bound. So, only when the bus supports user VA > > > (e.g. vhost-vdpa). > > > > > > vdpasim_mm_work_fn work is used to serialize the binding to a new > > > address space when the .bind_mm callback is invoked, and unbinding > > > when the .unbind_mm callback is invoked. > > > > > > Call mmget_not_zero()/kthread_use_mm() inside the worker function > > > to pin the address space only as long as needed, following the > > > documentation of mmget() in include/linux/sched/mm.h: > > > > > > * Never use this function to pin this address space for an > > > * unbounded/indefinite amount of time. > > > > I wonder if everything would be simplified if we just allow the parent > > to advertise whether or not it requires the address space. > > > > Then when vhost-vDPA probes the device it can simply advertise > > use_work as true so vhost core can use get_task_mm() in this case? > > IIUC set user_worker to true, it also creates the kthread in the vhost > core (but we can add another variable to avoid this). > > My biggest concern is the comment in include/linux/sched/mm.h. > get_task_mm() uses mmget(), but in the documentation they advise against > pinning the address space indefinitely, so I preferred in keeping > mmgrab() in the vhost core, then call mmget_not_zero() in the worker > only when it is running. > > In the future maybe mm will be used differently from parent if somehow > it is supported by iommu, so I would leave it to the parent to handle > this. > > Thanks, > Stefano I think iommufd is supposed to handle all this detail, yes. 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Tsirkin" To: Stefano Garzarella Subject: Re: [PATCH v3 8/8] vdpa_sim: add support for user VA Message-ID: <20230323074427-mutt-send-email-mst@kernel.org> References: <20230321154804.184577-1-sgarzare@redhat.com> <20230321154804.184577-4-sgarzare@redhat.com> <20230323095006.jvbbdjvkdvhzcehz@sgarzare-redhat> MIME-Version: 1.0 In-Reply-To: <20230323095006.jvbbdjvkdvhzcehz@sgarzare-redhat> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Cc: Andrey Zhadchenko , kvm@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, eperezma@redhat.com, stefanha@redhat.com X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: base64 Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" T24gVGh1LCBNYXIgMjMsIDIwMjMgYXQgMTA6NTA6MDZBTSArMDEwMCwgU3RlZmFubyBHYXJ6YXJl bGxhIHdyb3RlOgo+IE9uIFRodSwgTWFyIDIzLCAyMDIzIGF0IDExOjQyOjA3QU0gKzA4MDAsIEph c29uIFdhbmcgd3JvdGU6Cj4gPiBPbiBUdWUsIE1hciAyMSwgMjAyMyBhdCAxMTo0OOKAr1BNIFN0 ZWZhbm8gR2FyemFyZWxsYSA8c2dhcnphcmVAcmVkaGF0LmNvbT4gd3JvdGU6Cj4gPiA+IAo+ID4g PiBUaGUgbmV3ICJ1c2VfdmEiIG1vZHVsZSBwYXJhbWV0ZXIgKGRlZmF1bHQ6IHRydWUpIGlzIHVz ZWQgaW4KPiA+ID4gdmRwYV9hbGxvY19kZXZpY2UoKSB0byBpbmZvcm0gdGhlIHZEUEEgZnJhbWV3 b3JrIHRoYXQgdGhlIGRldmljZQo+ID4gPiBzdXBwb3J0cyBWQS4KPiA+ID4gCj4gPiA+IHZyaW5n aCBpcyBpbml0aWFsaXplZCB0byB1c2UgVkEgb25seSB3aGVuICJ1c2VfdmEiIGlzIHRydWUgYW5k IHRoZQo+ID4gPiB1c2VyJ3MgbW0gaGFzIGJlZW4gYm91bmQuIFNvLCBvbmx5IHdoZW4gdGhlIGJ1 cyBzdXBwb3J0cyB1c2VyIFZBCj4gPiA+IChlLmcuIHZob3N0LXZkcGEpLgo+ID4gPiAKPiA+ID4g dmRwYXNpbV9tbV93b3JrX2ZuIHdvcmsgaXMgdXNlZCB0byBzZXJpYWxpemUgdGhlIGJpbmRpbmcg dG8gYSBuZXcKPiA+ID4gYWRkcmVzcyBzcGFjZSB3aGVuIHRoZSAuYmluZF9tbSBjYWxsYmFjayBp cyBpbnZva2VkLCBhbmQgdW5iaW5kaW5nCj4gPiA+IHdoZW4gdGhlIC51bmJpbmRfbW0gY2FsbGJh Y2sgaXMgaW52b2tlZC4KPiA+ID4gCj4gPiA+IENhbGwgbW1nZXRfbm90X3plcm8oKS9rdGhyZWFk X3VzZV9tbSgpIGluc2lkZSB0aGUgd29ya2VyIGZ1bmN0aW9uCj4gPiA+IHRvIHBpbiB0aGUgYWRk cmVzcyBzcGFjZSBvbmx5IGFzIGxvbmcgYXMgbmVlZGVkLCBmb2xsb3dpbmcgdGhlCj4gPiA+IGRv Y3VtZW50YXRpb24gb2YgbW1nZXQoKSBpbiBpbmNsdWRlL2xpbnV4L3NjaGVkL21tLmg6Cj4gPiA+ IAo+ID4gPiAgICogTmV2ZXIgdXNlIHRoaXMgZnVuY3Rpb24gdG8gcGluIHRoaXMgYWRkcmVzcyBz cGFjZSBmb3IgYW4KPiA+ID4gICAqIHVuYm91bmRlZC9pbmRlZmluaXRlIGFtb3VudCBvZiB0aW1l Lgo+ID4gCj4gPiBJIHdvbmRlciBpZiBldmVyeXRoaW5nIHdvdWxkIGJlIHNpbXBsaWZpZWQgaWYg d2UganVzdCBhbGxvdyB0aGUgcGFyZW50Cj4gPiB0byBhZHZlcnRpc2Ugd2hldGhlciBvciBub3Qg aXQgcmVxdWlyZXMgdGhlIGFkZHJlc3Mgc3BhY2UuCj4gPiAKPiA+IFRoZW4gd2hlbiB2aG9zdC12 RFBBIHByb2JlcyB0aGUgZGV2aWNlIGl0IGNhbiBzaW1wbHkgYWR2ZXJ0aXNlCj4gPiB1c2Vfd29y ayBhcyB0cnVlIHNvIHZob3N0IGNvcmUgY2FuIHVzZSBnZXRfdGFza19tbSgpIGluIHRoaXMgY2Fz ZT8KPiAKPiBJSVVDIHNldCB1c2VyX3dvcmtlciB0byB0cnVlLCBpdCBhbHNvIGNyZWF0ZXMgdGhl IGt0aHJlYWQgaW4gdGhlIHZob3N0Cj4gY29yZSAoYnV0IHdlIGNhbiBhZGQgYW5vdGhlciB2YXJp YWJsZSB0byBhdm9pZCB0aGlzKS4KPiAKPiBNeSBiaWdnZXN0IGNvbmNlcm4gaXMgdGhlIGNvbW1l bnQgaW4gaW5jbHVkZS9saW51eC9zY2hlZC9tbS5oLgo+IGdldF90YXNrX21tKCkgdXNlcyBtbWdl dCgpLCBidXQgaW4gdGhlIGRvY3VtZW50YXRpb24gdGhleSBhZHZpc2UgYWdhaW5zdAo+IHBpbm5p bmcgdGhlIGFkZHJlc3Mgc3BhY2UgaW5kZWZpbml0ZWx5LCBzbyBJIHByZWZlcnJlZCBpbiBrZWVw aW5nCj4gbW1ncmFiKCkgaW4gdGhlIHZob3N0IGNvcmUsIHRoZW4gY2FsbCBtbWdldF9ub3RfemVy bygpIGluIHRoZSB3b3JrZXIKPiBvbmx5IHdoZW4gaXQgaXMgcnVubmluZy4KPiAKPiBJbiB0aGUg ZnV0dXJlIG1heWJlIG1tIHdpbGwgYmUgdXNlZCBkaWZmZXJlbnRseSBmcm9tIHBhcmVudCBpZiBz b21laG93Cj4gaXQgaXMgc3VwcG9ydGVkIGJ5IGlvbW11LCBzbyBJIHdvdWxkIGxlYXZlIGl0IHRv IHRoZSBwYXJlbnQgdG8gaGFuZGxlCj4gdGhpcy4KPiAKPiBUaGFua3MsCj4gU3RlZmFubwoKSSB0 aGluayBpb21tdWZkIGlzIHN1cHBvc2VkIHRvIGhhbmRsZSBhbGwgdGhpcyBkZXRhaWwsIHllcy4K Cl9fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fClZpcnR1YWxp emF0aW9uIG1haWxpbmcgbGlzdApWaXJ0dWFsaXphdGlvbkBsaXN0cy5saW51eC1mb3VuZGF0aW9u Lm9yZwpodHRwczovL2xpc3RzLmxpbnV4Zm91bmRhdGlvbi5vcmcvbWFpbG1hbi9saXN0aW5mby92 aXJ0dWFsaXphdGlvbg==