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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS 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 29E7FC43381 for ; Tue, 19 Feb 2019 20:17:48 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F3B7320851 for ; Tue, 19 Feb 2019 20:17:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729554AbfBSURq (ORCPT ); Tue, 19 Feb 2019 15:17:46 -0500 Received: from mail-qk1-f196.google.com ([209.85.222.196]:39375 "EHLO mail-qk1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726110AbfBSURp (ORCPT ); Tue, 19 Feb 2019 15:17:45 -0500 Received: by mail-qk1-f196.google.com with SMTP id x6so508582qki.6 for ; Tue, 19 Feb 2019 12:17:44 -0800 (PST) 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; bh=kCcuAPQu7uM1twjELqEskJaLGGZmSZUiGg97ChszaOQ=; b=q63Q6mJTKtCgdO0Jr/ovUu/y2yWenDaWuZQg21YlRmbjIXSc4xOFC4AsjTnSFIa9tJ 5c4viefShuauwswDueD0x3Tk82slrMK4VEvgZJyrZVVAHT8+JNKdlUCw7SQdUH19FsSU JtSVRyrgV2f2dnhCxErJ1rp2gc2dz/KCwTlmqz7tGYDd4W2t4K2Y7wrDyBFI6okdpIXm bJBbrR5YDBIHWUay+GYrBWPLCtYuKsn9pNzxtFpuf88JjiXxbPVb9e+ASSuyPQsg5vXQ Fh0n+lphNEjqCakQKQZ0k6q2U45tKIqSvQvQh7VO1B/NVQVgM7ptRjMaaoWN+6Uvtjy4 dYWA== X-Gm-Message-State: AHQUAubU+kupYOgq7mkf5neWtGInIVmmBn4CeT0Uq4oOP1+fvlct0401 VlZMKNMKO5YnPQcJV6mbFNPKgA== X-Google-Smtp-Source: AHgI3IYN0a3df1axZWdu8fr7a1cy+OK+ivSSggslX/I2TMxGVQWcq2AxyxqRLlJrR3dsugFlWN+EtQ== X-Received: by 2002:a37:c505:: with SMTP id p5mr22148960qki.257.1550607463215; Tue, 19 Feb 2019 12:17:43 -0800 (PST) Received: from redhat.com (pool-173-76-246-42.bstnma.fios.verizon.net. [173.76.246.42]) by smtp.gmail.com with ESMTPSA id f33sm11359847qta.91.2019.02.19.12.17.41 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 19 Feb 2019 12:17:42 -0800 (PST) Date: Tue, 19 Feb 2019 15:17:40 -0500 From: "Michael S. Tsirkin" To: David Hildenbrand Cc: Alexander Duyck , Nitesh Narayan Lal , kvm list , LKML , Paolo Bonzini , lcapitulino@redhat.com, pagupta@redhat.com, wei.w.wang@intel.com, Yang Zhang , Rik van Riel , dodgen@google.com, Konrad Rzeszutek Wilk , dhildenb@redhat.com, Andrea Arcangeli Subject: Re: [RFC][Patch v8 0/7] KVM: Guest Free Page Hinting Message-ID: <20190219151552-mutt-send-email-mst@kernel.org> References: <20190218143819-mutt-send-email-mst@kernel.org> <58714908-f203-0b64-845b-5818e52a62fa@redhat.com> <20190218152021-mutt-send-email-mst@kernel.org> <18d87846-72c7-adf0-5ca3-7312540bb31b@redhat.com> <478a9574-a604-0aa9-d569-6a5cd98d7cdc@redhat.com> <77e71dc3-640b-bbf6-6a47-bb2371c06172@redhat.com> <20190219145241-mutt-send-email-mst@kernel.org> <0118482c-e633-3949-6797-94d7deb8a382@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <0118482c-e633-3949-6797-94d7deb8a382@redhat.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 19, 2019 at 09:02:52PM +0100, David Hildenbrand wrote: > On 19.02.19 20:58, Michael S. Tsirkin wrote: > > On Tue, Feb 19, 2019 at 10:06:35AM -0800, Alexander Duyck wrote: > >>> I tend to like an asynchronous reporting approach as discussed in this > >>> thread, we would have to see if Nitesh could get it implemented. > >> > >> I agree it would be great if it could work. However I have concerns > >> given that work on this patch set dates back to 2017, major issues > >> such as working around device assignment have yet to be addressed, > > > > BTW for device assignment to work, your idea of sending > > data directly to kvm won't work, will it? > > You need to update userspace so it can update VFIO right? > > Another blocker for assignment is ability to make holes > > an an existing mapping - supported by hardware but > > not by IOMMU drivers. > > I had the exact same thought and then realized that we decided to block > the balloon in user space until we figured out how to handle this properly. > > I wonder if MADV_FREE behaves differently compared to MADV_DONTNEED when > finding pinned pages, but I doubt it. Most probably we'll have to > disable hinting for device assignments as well. OK but let's recognize it as a bug not a feature. -- MST