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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 1F637C79FB6 for ; Wed, 9 Sep 2026 15:35:17 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id DB2B56B0096; Wed, 9 Sep 2026 11:35:15 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D8A4E6B0098; Wed, 9 Sep 2026 11:35:15 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C529A6B0099; Wed, 9 Sep 2026 11:35:15 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 8FE9A6B0096 for ; Wed, 9 Sep 2026 11:35:15 -0400 (EDT) Received: from smtpin17.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay06.hostedemail.com (Postfix) with ESMTP id C9ECEA42E2 for ; Wed, 9 Sep 2026 15:35:14 +0000 (UTC) X-FDA: 85194622548.17.B1F7EC8 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf02.hostedemail.com (Postfix) with ESMTP id F10788000D for ; Wed, 9 Sep 2026 15:35:12 +0000 (UTC) Authentication-Results: imf02.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=ckd3bN3Z; spf=pass (imf02.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1788968113; h=from:from:sender: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:dkim-signature; bh=xj5P1Cjd9irB4BUOsfOHGIxVo3gJHi6q3o3BRLAUlrM=; b=LPUM6a+6TxcNFoixPm/i2/uFCppf/zvkkPm6npix73pMvwVs5znlxQkKT/3u0Wv1iyJuq1 4dIJo1MlE2z5P71PW8xlOgBhI/VL0T2vByuJOaq3bbwQJL1f8GWssLc89Th4hZDxYXhK9D 16sT946rCbTvR/dJhIQDj69R51FOlvs= ARC-Authentication-Results: i=1; imf02.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=ckd3bN3Z; spf=pass (imf02.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1788968113; b=EABr3459ZHsDMyuqV1yS7p+BvLJ2QWZfJQZfKJuVg/h3W1bkvP4Aou959K2pkB4Ph2o3eE nNE+16GiTJ4tY9GEQh3Xz5MyH8xDPiLbj8ubD8dAxzHKcpmZJ3yht/qJf8Kbnm12vLNjtz TYKgrWoR4hV4Bpmf0O2NYD/oTmGT93o= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 0BB4341954; Wed, 9 Sep 2026 15:35:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 191301F00A3D; Wed, 9 Sep 2026 15:34:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788968111; bh=xj5P1Cjd9irB4BUOsfOHGIxVo3gJHi6q3o3BRLAUlrM=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=ckd3bN3ZBsVSMEnnFHviWt7dllTHTgykVYrIZMkd7W2vUKKUCgePCf65XS2sM98lX Qre8UzhEfTBMyw5wJ5X+7M/4kE5evGsK7cd1QkWeCxNvzqPpxbWg4ehHniu+1/ykw0 asx5+MVfKRElxSINUvPSkNJDcreFgZEOBrSHVP0Kc6H2/aVk5HftReDcq4lNZUgjhV lpLgubOZFtll6VhDJCF4y+SOJuXrn9nSKAxyFQ/jogDZ1vVjkiAhpxZgKYZjEpPZKg K8EqCmZYf+jj2635P6MAVMgB9x/Gk/vRISsyVa4GSF4qweNESa7itJUAurLqwjkmdZ tqivnhL9dbvhA== Message-ID: Date: Wed, 9 Sep 2026 17:34:48 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v12 01/45] KVM: guest_memfd: Optimize away conversion overheads via dead-code elimination To: ackerleytng@google.com, aik@amd.com, andrew.jones@linux.dev, binbin.wu@linux.intel.com, brauner@kernel.org, chao.p.peng@linux.intel.com, jmattson@google.com, jthoughton@google.com, michael.roth@amd.com, oupton@kernel.org, pankaj.gupta@amd.com, qperret@google.com, rick.p.edgecombe@intel.com, rientjes@google.com, shivankg@amd.com, steven.price@arm.com, willy@infradead.org, wyihan@google.com, yan.y.zhao@intel.com, forkloop@google.com, pratyush@kernel.org, suzuki.poulose@arm.com, aneesh.kumar@kernel.org, liam@infradead.org, Paolo Bonzini , Sean Christopherson , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Steven Rostedt , Masami Hiramatsu , Mathieu Desnoyers , Jonathan Corbet , Shuah Khan , Shuah Khan , Vishal Annapurve , Andrew Morton , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Youngjun Park , Qi Zheng , Shakeel Butt , Kiryl Shutsemau , Baoquan He , Jason Gunthorpe , John Hubbard , Peter Xu , tarunsahu@google.com, Randy Dunlap , Lorenzo Stoakes , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Fuad Tabba Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-coco@lists.linux.dev References: <20260830-gmem-inplace-conversion-v12-0-85e5fd25252a@google.com> <20260830-gmem-inplace-conversion-v12-1-85e5fd25252a@google.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260830-gmem-inplace-conversion-v12-1-85e5fd25252a@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: 4o38k645ht34sa4cktnsxbcuj5y7exek X-Rspamd-Queue-Id: F10788000D X-Rspamd-Server: rspam07 X-HE-Tag: 1788968112-176829 X-HE-Meta: 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 03kw9pTS KAj2GeArRC28N2waGR1Fk9vayfYfFXw/zpB04EtufBPFG2DIIavEv+6C3HGDq41C4keuz/0OD64PHyLsK2zsY9kBbQHV+D5f5iio3BDakf9V8l3V51yZJ0ZkhyyhpXbzCtMyoxA4Q4RvNRX+SkFNqg7deCNkddWx4BA7ZL3RgltAEeCwBbSKkBRg3lhfoq7Zr2RqIhctHTa9aTAE5HUen+5Laiy/kfYaWUQ05QOT+ccUkos3L9OoV4Cg6aoP5RC3ZM5AXDTZcmBDNYmENsPlmeKyIygtmxGIrdwZsz8+RIM/HFHEsqZFEQUdLYZoaGjuhZy5YnhnCFFV1KDtmRboqBOxwJw6UbXpMhH7/fO+ylJzxbghzTaenPUWbU6sOh6nod06X Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 8/31/26 02:25, Ackerley Tng via B4 Relay wrote: > From: Sean Christopherson > > Add and use kvm_arch_has_gmem_convert() to guard guest_memfd's invocation > of arch hooks related to converting memory between private and shared, as > only one half of the x86 CoCo duo needs the runtime hooks (any pre-work is > pure overhead for TDX). At this exact moment, the overhead is negligible, > but that will change when in-place conversion comes along, at which point > to-shared conversions will "need" to find all affected folios prior to > calling into arch code. In quotes because very technically that work could > be pushed to arch code, but that would bleed guest_memfd details into arch > code and would be far worse than adding yet another kvm_arch_has... hook. > > Opportunistically provide the kvm_arch_gmem_make_private() declaration, and > rely on dead-code elimination to eliminate the call to non-existent code > when CONFIG_HAVE_KVM_ARCH_GMEM_CONVERT=n. > > Reported-by: Binbin Wu > Closes: https://lore.kernel.org/all/1ec08cd8-3072-4753-ad5e-cd34956647f8@linux.intel.com > Suggested-by: Ackerley Tng > Signed-off-by: Sean Christopherson > Signed-off-by: Ackerley Tng > --- Reviewed-by: David Hildenbrand (Arm) -- Cheers, David