From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 76C6D3403ED; Mon, 8 Jun 2026 11:09:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780916951; cv=none; b=MybSBZptvKZA+UUhjmFEXaP/oKtvbqc9pZSTtWq7bf9Lec7ks6LXpOCCuccpiy29JaKMhIZhhkUwIkAk9YuX5DGwvSz0laquMo5yiWUDbeGRldn5ih1scf2xwzttmrbTcRqyvSqkZOX6/y2TmTtvXSZ9ubD8e7foNl0/4MHq63o= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780916951; c=relaxed/simple; bh=NGBeHT/GiMcQQALei4OwNpbycWZ+b9m7PzS+SYcHQFA=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=DjoGDP8lnczy3M83mgBRyv404EpeykWhDgPww2yx7/f5/86aJmkiE7Pg6PSLCx6RGxgqSHqaeqKHctLNbDRJq08jkZUNSNYChMAZzOhA1hh6lrMHRixp/KyqNdOafKos1riS7pKo7Z1r2ABw8sedkGAba8LhPz2LzCr7MaYeOk0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=HICbOiY7; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="HICbOiY7" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C6CE01F00893; Mon, 8 Jun 2026 11:08:59 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1780916950; bh=hc/qlM6AXIf4NHvVFYTmMogdhCS062x3B65dfP/PPwY=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=HICbOiY7mVbZABlmQS9r9qxSDVd/U5vhNVSwfuvEYMuSXCDxThNC+OThT/sW7pI/Y ZNwf/7wqg2v+asEQ4fo+4BsLfxEEqZLyca4ZRdsvC/fhmaO4LN0v5TOM/QL4FMZwmJ c0qC2GensuPyio1c7c88eZCj6BA4v7o6G7meAwBVRvSpxZ8EBV/fk17JzfHjOPq7LA 6+HbwLmLo9OjxiIoXNHtg7TXg8KKXfBA6Mm7B8B3qaHbEpsGe2g49jR32+2ToprIET 8DDevnn++18AFDXzmqdD86E1aRclyGxJ6pf8ipz8AqwUv0jz+4Ggd+HsdP5HsPU9zk rKeeRLezEcRdg== Message-ID: <64f2e580-aa82-4849-9236-b8ec4208ca24@kernel.org> Date: Mon, 8 Jun 2026 13:08:57 +0200 Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v10 07/37] mm: thread user_addr through page allocator for cache-friendly zeroing To: Lorenzo Stoakes , "Michael S. Tsirkin" Cc: linux-kernel@vger.kernel.org, Jason Wang , Xuan Zhuo , =?UTF-8?Q?Eugenio_P=C3=A9rez?= , Muchun Song , Oscar Salvador , Andrew Morton , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Hugh Dickins , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Gregory Price , Ying Huang , Alistair Popple , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , Axel Rasmussen , Yuanchu Xie , Wei Xu , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , virtualization@lists.linux.dev, linux-mm@kvack.org, Andrea Arcangeli References: <50d410b47fe3f45327783e05bd306d5eaab75e65.1780906288.git.mst@redhat.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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/8/26 12:23, Lorenzo Stoakes wrote: > I noticed this patch, again, sneaks in some additional code changes that > are not mentioned in the commit message and seem irrelevant to the patch. > > Not sure if the AI is doing this, but please don't do that. > > On Mon, Jun 08, 2026 at 04:35:17AM -0400, Michael S. Tsirkin wrote: >> Thread a user virtual address from vma_alloc_folio() down through >> the page allocator to post_alloc_hook(). This is plumbing >> preparation for a subsequent patch that will use user_addr to >> call folio_zero_user() for cache-friendly zeroing of user pages. > > This feels like very weak justification for code that massively changes mm > code and makes it all much worse. > >> >> The user_addr is stored in struct alloc_context and flows through: >> vma_alloc_folio -> folio_alloc_mpol -> __alloc_pages_mpol -> >> __alloc_frozen_pages -> get_page_from_freelist -> prep_new_page -> >> post_alloc_hook > > Is this the only relevant code path? You're changing a TON of code here > that will have multiple different code paths? > >> >> USER_ADDR_NONE ((unsigned long)-1) is used for non-user >> allocations, since address 0 is a valid userspace mapping. > > Ugh god, so now we're passing a user address through allocation paths that > might not even be aware of this or be allocating memory at a point when the > mapping is known? The original ideas was to do this only with internal interfaces. I think I raised before to leave hugetlb alone for now. Fundamentally, user_alloc_needs_zeroing() is something we should get rid of, to just be able use __GFP_ZERO and do zeroing at exactly one place. The question is how to pass that information (user_addr) through internal APIs. I previously said, that ideally we'd end up with a folio allocation interface in mm/page_alloc.c, from where we could get this done more cleanly internally. But I don't want what the previous proposals did: use GFP flags+leak state or return magic "zeroed" flags. -- Cheers, David