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 5C267C43381 for ; Tue, 19 Feb 2019 19:59:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2C50E20700 for ; Tue, 19 Feb 2019 19:59:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729344AbfBST67 (ORCPT ); Tue, 19 Feb 2019 14:58:59 -0500 Received: from mail-qk1-f196.google.com ([209.85.222.196]:38550 "EHLO mail-qk1-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729058AbfBST65 (ORCPT ); Tue, 19 Feb 2019 14:58:57 -0500 Received: by mail-qk1-f196.google.com with SMTP id p15so472278qkl.5 for ; Tue, 19 Feb 2019 11:58:56 -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=nxj+G0sNKNaSYFN6jDA8KSosnNrPgcvqT9FcW0DMnlM=; b=q4Fir75PJatoHXmPN2KI7gP+kVhb91JrsZaFTkKsaAVZMAEGSN3OVHyyojHEBCU5Ki xzu0RQ3MMmiQaBWhmSEK3vKsVxH5f8BCwiS0U8Jqra1cgkgsyT5CcAjVL26pVixSX1wN v49hBiaSZ1YPJ/508A/E8xAVCTHqntKh2ZCnsmo2QmhTxamrUwXqLGBSURZDchNhfbrQ e9GLrE0B5opAGNtnWYapkzz9uOUyQkPTY0wU8U9x0sRnbhkwSn/wrCzi61rEUq/UmNPE DhYjMLzJBu2TrESNDbVAzDdimin+zuAikOXIa0+AWDeOgw7A2kdzViFsjonfBmrRBqP4 ehSA== X-Gm-Message-State: AHQUAuYYss96g7oPxSaVF5Ol4Fk6vs4t6CYsFuSjL63V1fVGX5g6QHq4 aL4oVSW/h/xEt7bWhKI51pZYFw== X-Google-Smtp-Source: AHgI3IbgQHxNgMz3z/gbEtLOCqAcVJDwkK7wDfo3qNI4Pn2T7WhTVAPQEybnQ/RkhDiCm1lbER3dpg== X-Received: by 2002:a37:aa0b:: with SMTP id t11mr21675517qke.241.1550606335110; Tue, 19 Feb 2019 11:58:55 -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 q25sm3490434qtk.73.2019.02.19.11.58.53 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Tue, 19 Feb 2019 11:58:54 -0800 (PST) Date: Tue, 19 Feb 2019 14:58:51 -0500 From: "Michael S. Tsirkin" To: Alexander Duyck Cc: David Hildenbrand , 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: <20190219145241-mutt-send-email-mst@kernel.org> References: <20190218140947-mutt-send-email-mst@kernel.org> <4039c2e8-5db4-cddd-b997-2fdbcc6f529f@redhat.com> <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> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 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. All the issues are shared with balloon btw, so that could be another reason to use the balloon. > and > it seems like most of the effort is being focused on things that in my > opinion are being over-engineered for little to no benefit. > > I really think that simpler would be much better in terms of design in > this case. > > Thanks. > > - Alex I personally learned a lot from Wei's work on hinting. All this doesn't mean you approach is not the right one. -- MST