From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 7307B360ECC for ; Tue, 12 May 2026 11:44:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778586241; cv=none; b=WkmV2Zo9X2GsDv20xe7C7XuQCioRyMWNCZW48MDDW2fxf+pS4oViJCc6dtnoIan6vbZ+0RGiAnWvZ9ErZ5vDxD4M72JyGySfMOavdeE0qoUmiiikeufgYYtN75xbImSE1bc8KDej7VbfrFW/6syhsNne4nCaTCFpAZMQo5iHHWs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778586241; c=relaxed/simple; bh=H+ti7zY/i4rnciLzAJI+9KovwD+hoVGMIVTnLhNKeX8=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=GLzZavr71MaL60x1Da3d47BEMW1CHAgPuvmH4ROJS51JocL6Gal5uno8V91i0j+OILj2kk7LZwSPwv5cMRz0KLxiYut0Nabs04Hm0y724O3r6md5UezdpeC8zJQQpAm25G5WGTkL4lqy5kh6wqF93yCypHOQo9U8efpNxvwTQHg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=m+1IZa7R; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="m+1IZa7R" 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 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 > + > +/** > + * 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