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 DDC5EC79FB6 for ; Wed, 9 Sep 2026 15:40:25 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D75D16B0099; Wed, 9 Sep 2026 11:40:24 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id D1F266B009B; Wed, 9 Sep 2026 11:40:24 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C0DAA6B009D; Wed, 9 Sep 2026 11:40:24 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 8E7296B0099 for ; Wed, 9 Sep 2026 11:40:24 -0400 (EDT) Received: from smtpin08.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 2946CA01B3 for ; Wed, 9 Sep 2026 15:40:24 +0000 (UTC) X-FDA: 85194635568.08.4EE02A9 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf23.hostedemail.com (Postfix) with ESMTP id 50037140010 for ; Wed, 9 Sep 2026 15:40:22 +0000 (UTC) Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=b67FWDHV; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf23.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Authentication-Results: i=1; imf23.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=b67FWDHV; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf23.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1788968422; b=WFQWTL5fC4OLDMSv45/ozX37YkVwCsRPAw7w4M6mM/CCRl80Jc2q/kRJH/KrM68KDC+Hkn 4qX19yxUVWfXyCwHzPog2ZQuioiOPCkHa6qkALqV4eH74lAkEOU2hvVRjgGTtKHmIQkqHM EPPlpWUIIik2O86BhHUhVBV2Bqa7CEA= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1788968422; 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=AXYYQlIGAZBrAHu4CUr6VQDiXrusLKFHKO4tw/xbR/o=; b=jyI4cFVQWrh3mbZuEr/UgadUElD5ktVEtIyhVzT2fqdm9S+24F6GN+3ko3rQO2JKINp6tQ nYfAQjg5zjwsCvLVsOrUC14QKngYXe8GSJ964oe2VO5e5T/kblagm/9kQ9CX2JMnGCFhbf TxEP+5QoBDcR4c8bH1oEvdzTLtmaxTE= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 60D8341443; Wed, 9 Sep 2026 15:40:21 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DE5D41F00A3A; Wed, 9 Sep 2026 15:40:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788968421; bh=AXYYQlIGAZBrAHu4CUr6VQDiXrusLKFHKO4tw/xbR/o=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=b67FWDHVrvKlADudVooPhLmJOQAbQa4r/JfwC9gUSiN2XwdjDzXh8PDhLIbwBJ2Bl N6Vzk3XSxn9iwept0h4EbsT1QjEwa1ArTZoWsrAUs3sRxTkLtG3u6Tqn48pqVF4w42 Hbr0VynPh2dln0S6/KgjarMmfPtDZf/8puPSLa3d6dAowUIbor3F3E8wZW4gfkHAy7 ioBnUGH/HGUgh73jIHLXiP9er2c5LG71oVhLkOGVgFSr+kjgVMlPqHXLGlxCQA7ZS5 LcMe5V5KBReJ3ihsKdA8eubDNI8HqYBjN9XKnu0HuBHiiD05yVhAVNYtvLFO27T70K 2JOkNN9/OsV+Q== Message-ID: <26f620c7-043a-4cb3-a74b-29069bded0dd@kernel.org> Date: Wed, 9 Sep 2026 17:40:00 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v12 12/45] KVM: guest_memfd: Always fault from guest_memfd if in-place conversion is enabled 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-v12-12-85e5fd25252a@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-v12-12-85e5fd25252a@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: 50037140010 X-Stat-Signature: 3mur5rxy14xz1wuhf63i9ynyrtafzoz5 X-Rspamd-Server: rspam01 X-HE-Tag: 1788968422-310504 X-HE-Meta: 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 Um8G77nA eOnH4V/Z+doX2bz8CB5+eBgTeDdTE/OjRpsPmybVh9XNJPpHhZjxBjUumxSuIX6A4SPj97alYGQZKr7xUsD1j5uXZ+BNYcTbEnx656fs1jELKqDHFLDIEkYw11ZyMOBlA3jLt3Pwr8LmmqUoz53zL6E/Smff2XTj4Bi6I8cl+OQJC0OtVUTEcq28cP3CTf7r2lYWBp/nE3CgCoM5vv/izCWg9i0ePTRYPZxPRlliv5eqHU6d71wrO3vEk0gpGA5MRqtI9bk2kHrsm5JLi+cDRtJlfWKjFMGwMNUotHREEuOxOaitIMeAT8d07yKrmCVRZjBnQA394vXIdm/rAt6Nf2SLIsgrzAGhvfnWT 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: Ackerley Tng > > If a guest_memfd memslot is created but the guest_memfd does not have the > GUEST_MEMFD_FLAG_MMAP set, KVM still fulfils guest faults by looking up the > memslot's userspace_addr. > > Set KVM_MEMSLOT_GMEM_ONLY if in-place conversion is enabled so that the > guest_memfd's memory will be used for both shared and private memory. With > in-place conversion, guest_memfd will be the only backing memory for the > memslot. > > No validation is performed to require userspace_addr to be a mapping from > the associated guest_memfd because even after validation, userspace is free > to remap something else at the provided userspace_addr. > > userspace_addr will still be used by functions like kvm_read_guest(), and > if userspace_addr does not match up with the corresponding memory in the > memslot's guest_memfd (whether userspace_addr points to the wrong offset or > some non-guest_memfd memory, etc), that is a user error. > > Requiring both shared and private memory to come from the only associated > guest_memfd simplifies invalidation in stage 2 page tables. On a PUNCH_HOLE > operation on a guest_memfd, the invalidation is now guaranteed to be > invalidating only memory mapped from the given guest_memfd. > > Suggested-by: Sean Christopherson > Signed-off-by: Ackerley Tng > --- Yeah, that matches what we discussed in the call Reviewed-by: David Hildenbrand (Arm) -- Cheers, David