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 lists1p.gnu.org (lists1p.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3738FC88E53 for ; Fri, 11 Sep 2026 16:02:08 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists1p.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1x53h0-0001lF-LJ; Fri, 11 Sep 2026 12:01:34 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists1p.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1x53gZ-0001bn-MN for qemu-devel@nongnu.org; Fri, 11 Sep 2026 12:01:13 -0400 Received: from sea.source.kernel.org ([172.234.252.31]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1x53gX-0006RI-Bk for qemu-devel@nongnu.org; Fri, 11 Sep 2026 12:01:07 -0400 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 4C50B41767; Fri, 11 Sep 2026 16:01:02 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5778B1F000FF; Fri, 11 Sep 2026 16:00:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1789142462; bh=l7vRwotPibZR4LJ8O22moZNG54W0TPohdxC+Q7VvvMw=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=a6vMfPnwUz2Q5vm0lUd6gzhAAI2ryNOrG2Eo5TJRVZyEXZyGrCG2Jj2siWVGeZYwq bXQBqtfUN1X23Y0+SHbPBTvEkolKrdxQIE42A3WRHryFxqixeTMTktVglqXQ1Kvo/s T6WBF7HfePMDVrYomK52VTBb97G+PmgKIkodB1f+MUfL/0lXIxcWsWNd7EopdpfT/G C69aQU0TpfniDOxu2wUkvbMwqf75qMjdeW0nV4DNG1PaQj3ZmtuVjkaIgwz50aBbjW PNfAWcSGm78Q0+um40a2IAcHTrArbuBDd1Iw0hK5bHTyxhsVzQPnbZqdRlSTDaJWpT nk5c1Rm67lntw== Message-ID: <26dd141c-fed3-4f7e-81db-315e975cdcd7@kernel.org> Date: Fri, 11 Sep 2026 18:00:56 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 08/12] hostmem: Support fully shared guest memfd to back a VM To: Peter Xu , Michael Roth Cc: qemu-devel@nongnu.org, pbonzini@redhat.com, berrange@redhat.com, armbru@redhat.com, pankaj.gupta@amd.com, isaku.yamahata@intel.com, xiaoyao.li@intel.com, chao.p.peng@linux.intel.com, Fabiano Rosas References: <20260908133151.836685-1-michael.roth@amd.com> <20260908133151.836685-9-michael.roth@amd.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit Received-SPF: pass client-ip=172.234.252.31; envelope-from=david@kernel.org; helo=sea.source.kernel.org X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: qemu development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On 9/11/26 14:06, Peter Xu wrote: > On Thu, Sep 10, 2026 at 06:00:11PM -0500, Michael Roth wrote: >> On Thu, Sep 10, 2026 at 10:54:09AM +0200, David Hildenbrand wrote: >>> >>> [...] >>> >>> >>> There is a lot of uncertainty how guest_memfd would consume huge pages. So best >>> to drop the "yet" that implies how it would be consumed (and that it would be >>> called "hugetlb"). >> >> Makes sense, will change this as suggested for v6 > > I'm just curious, any more info on this part? Any link to existing work > would help. Ackerley has been mostly busy doing the in-place conversion, the hugetlb-related patches he sent are a bit dated. He's been recently looking into how to abstract memory providers for guest_memfd, I think there were some upstream discussions related to that in related context: https://lore.kernel.org/r/CAEvNRgHbfx470HUBJhEUVKPKqsV0LnhX+wkD1TE-61fZy3jjUw@mail.gmail.com > > At least from our side, we look for hugetlb-alike support on gmem. I want > to make sure what I understand still is valid, and it is still open to > solve the postcopy problem. Right, something like that will come. And I am not saying that we won't model it as "guest memfd hugetlb" support in QEMU, but I wouldn't start documenting that it will be modeled like that. hugetlb will initially be used as a memory provider for hugetlb to allocate larger pages, and guest_memfd will essentially strip these pages from hugetlb details, turning them into simple large guest_memfd pages. One idea is to support other pools, where also hugetlb could take pages from these pools. So it's just a matter of "we don't know how we will model it, and we don't know whether it will be called hugetlb". -- Cheers, David