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 17BC5CD4F35 for ; Tue, 12 May 2026 11:44:06 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 324816B0088; Tue, 12 May 2026 07:44:05 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 2D5A76B008A; Tue, 12 May 2026 07:44:05 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1C46C6B008C; Tue, 12 May 2026 07:44:05 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id 09F436B0088 for ; Tue, 12 May 2026 07:44:05 -0400 (EDT) Received: from smtpin28.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 3629F40447 for ; Tue, 12 May 2026 11:44:04 +0000 (UTC) X-FDA: 84758584008.28.6AD5B4F Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf25.hostedemail.com (Postfix) with ESMTP id 4EBE1A0002 for ; Tue, 12 May 2026 11:44:02 +0000 (UTC) Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=m+1IZa7R; spf=pass (imf25.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=1778586242; 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=nn7VPtIsRtdRIew4Dgh4cBQx6Sy5ky9DqPFrkHvuB2g=; b=yw29TXqu2pwYrrMVpqwcgFJxLfVm6/g1BxcLA1XndTj3LkzRTCEyua6lRtv4d7M4fJklGT qGEu7HebmdFiSLvfEgAZ/O+MO+rblKnHeOUPeZ4/SzRwP4YrsBWq2D0C/ZoKlAySl5kns/ DYanViFiDbupZTVBjVaESpr1RqS8GFg= ARC-Authentication-Results: i=1; imf25.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=m+1IZa7R; spf=pass (imf25.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; s=arc-20220608; d=hostedemail.com; t=1778586242; a=rsa-sha256; cv=none; b=2GV07j3CjAJzaz7+yFky7j5S61F02EOv0GCKLAuc66afRlRscjQm7BbbsgzZfW7pCv9s2S ys8jzIlgfwG5y3mpSdnDXK49Ij8nuqbAKphUpMl/OrBQtdVhEoaGG5Nwj0OtoERBP6F/XV NVSfWrcy5+32kJpcE84wK43GBI3yKAw= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 2271141913; Tue, 12 May 2026 11:44:01 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9CBF0C2BCB0; Tue, 12 May 2026 11:43:57 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778586241; bh=H+ti7zY/i4rnciLzAJI+9KovwD+hoVGMIVTnLhNKeX8=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=m+1IZa7Rz8qrTSMnetT0o7flalUm6rwu31zjfmm1CRbRgqFCWMfUVmNAVBgYfwYYN Oto9ybQ+WxwnaTDUS8PSL3MCKBvNMW9dSqPlqK1ezYX6jCwFdlzHliB46QlG3OhSA4 7tNO5yw5uRZVhR3YMiDOy6uu/P5oX3gRGEZdQt2Bdeprx2s+mlExiSR4RY6JNZjyGY ByERcfRQRWYkZ3U15YvVWWYh1sl7STMcJ69dNWsuX1LLzJPVrtZJs2s+zqLwIrz+kd WIsQQ7HQjmh7RzVi6TyUSDyXzPd4JV+c1zuZXuODBrhOBN5NWo/nl1cVfHkhOyqBzf G+TPwEgcAur/g== Message-ID: <4a9c4170-c6b7-424c-969c-19240f07e46b@kernel.org> Date: Tue, 12 May 2026 13:43:55 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v10 2/5] mm: Add helper to convert HMM pfn to migrate pfn To: mpenttil@redhat.com, linux-mm@kvack.org Cc: dri-devel@lists.freedesktop.org, intel-xe@lists.freedesktop.org, linux-kernel@vger.kernel.org, Jason Gunthorpe , Leon Romanovsky , Alistair Popple , Balbir Singh , Zi Yan , Matthew Brost , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko References: <20260505184421.2324798-1-mpenttil@redhat.com> <20260505184421.2324798-3-mpenttil@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: <20260505184421.2324798-3-mpenttil@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: edtgg5fincz33ctx55t867qcwfhunm9b X-Rspamd-Queue-Id: 4EBE1A0002 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1778586242-300755 X-HE-Meta: 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 e3TVgIlF fuZbGz8BxRREu/ZY8voobUHL2rzfG1baB1KWoT545dp2vb4gmkOcoRnUvFCf+CrgGXaKeZYqtSYiij/fRyXTkOSympEE2tjDoltiBzxmPMO4rXRuH09DT/qcfi4maJxQDBrBn+asRKcXw0CiWhcgG5f9g8fUx8vXIBKKPvd5yvG+X5So/hBDAghBihEuE78PLXRKX/vurdGVCe67d+0d/p5gcVQkuLa1ozn7vb9+dNktI0tIFlL59B2sn6iVPgvGaCCCW Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > + > +/** > + * migrate_hmm_range_setup() - prepare to migrate a range of memory > + * @range: contains pointer to struct migrate_vma to be set up. > + * > + * When collecting has been done with hmm_range_fault(), this > + * should be called next, and completes range->migrate by > + * populating migrate->src[] and migrate->dst[] > + * using range->hmm_pfns[]. > + * Also, migrate->cpages and migrate->npages get initialized. > + * After migrate_hmm_range_setup(), range->migrate is good > + * for the rest of the migrate_vma_* flow. > + */ > +void migrate_hmm_range_setup(struct hmm_range *range) > +{ > + struct migrate_vma *migrate = range->migrate; > + > + if (!migrate) > + return; > + > + migrate->npages = (migrate->end - migrate->start) >> PAGE_SHIFT; > + migrate->cpages = 0; > + > + for (unsigned long i = 0; i < migrate->npages; i++) { > + unsigned long pfn = range->hmm_pfns[i]; > + > + /* > + * We are only interested in entries to be > + * migrated. > + */ > + if (!(pfn & HMM_PFN_MIGRATE)) { > + migrate->src[i] = 0; > + migrate->dst[i] = 0; > + continue; > + } > + > + migrate->cpages++; > + > + /* HMM_PFN_MIGRATE without HMM_PFN_VALID denotes the special zero page */ > + if (pfn & (HMM_PFN_VALID)) No need for () > + migrate->src[i] = migrate_pfn(page_to_pfn(hmm_pfn_to_page(pfn))) Is there no easier way to avoid going through a page? I guess you really just want "migrate_pfn(pfn & ~HMM_PFN_FLAGS)". Maybe add a hmm_pfn_to_pfn() helper that does the "pfn & ~HMM_PFN_FLAGS" ? > + | MIGRATE_PFN_MIGRATE; We (MM folks) usually put the | onto the previous line to then properly indent the second line migrate->src[i] = migrate_pfn(page_to_pfn(hmm_pfn_to_page(pfn))) | MIGRATE_PFN_MIGRATE; > + else > + migrate->src[i] = MIGRATE_PFN_MIGRATE; It might be cleaner to just set migrate->src[i] = 0; here and to unconditionally migrate->src[i] |= MIGRATE_PFN_MIGRATE; So you don't have the MIGRATE_PFN_MIGRATE on two paths. > + > + migrate->src[i] |= (pfn & HMM_PFN_WRITE) ? MIGRATE_PFN_WRITE : 0; > + migrate->src[i] |= (pfn & HMM_PFN_COMPOUND) ? MIGRATE_PFN_COMPOUND : 0; > + migrate->dst[i] = 0; > + } > + > + if (migrate->cpages) > + migrate_vma_unmap(migrate); Can you remind me why we do this here, in the setup() phase? The function doc does not really describe that. -- Cheers, David