From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (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 5C369223331 for ; Mon, 17 Feb 2025 14:30:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739802632; cv=none; b=Rw3aDBhYTqJrWku1Kkk/khcpXd9pCNU4PIjl6GHPln/mdqllI1nS3lrhCII2nIhMOezAkU4wCZZx5/6T+OzyceI8FJqLhFZ/UtzN1W9lvCwX+F6RSD/OpjINvn17Yqa670IqnSpgOlU6gLsMekbO4cUre2ZVedohPUpxyXma4MY= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739802632; c=relaxed/simple; bh=jpaKQCDdKqrCGqs5tcYeNWypUIvLvgmkvGlGr8cdj1w=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=c2mzwa2FNomfFv5rpZ9rq5aH1qcOH9u6h0gqluSCqDK1gXfRqU1pmHi0fkO6chp9qm4O/ugaMOTLi2CqYnqelxZQVxj6do2XPMAdvED6qzxiDT0h7Do6dQeRTtjOANcyB8i7bH1rxY1xOkqVxr8Z4dFLiqssGSzmF+XR7GRy7XE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=NYpqkRj7; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="NYpqkRj7" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1739802629; h=from:from: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:autocrypt:autocrypt; bh=TFLguTKriOEaEoNxtvT7MAJvdtieE227Ck7gm5fmJV0=; b=NYpqkRj7paELgjJIP8Yt7wWQrHtS63s8xltJKIwmPeB2NHiKjadsx5+OkxALVZYAN/kTUa ZkHuNENzE7CtAoiz3w9mR156x/uwzD8BLXDnjg7Q26h3UbVRchsQviPJ4D+BOWqSzsPafB nnew8HI9XYXILcHXzzBhAcB8X+aPTcc= Received: from mail-wm1-f71.google.com (mail-wm1-f71.google.com [209.85.128.71]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-280-JW-WEVW5NKK_aOmQblUstg-1; Mon, 17 Feb 2025 09:30:28 -0500 X-MC-Unique: JW-WEVW5NKK_aOmQblUstg-1 X-Mimecast-MFC-AGG-ID: JW-WEVW5NKK_aOmQblUstg_1739802627 Received: by mail-wm1-f71.google.com with SMTP id 5b1f17b1804b1-4388eee7073so27548975e9.0 for ; Mon, 17 Feb 2025 06:30:27 -0800 (PST) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1739802627; x=1740407427; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:from:references:cc:to:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=TFLguTKriOEaEoNxtvT7MAJvdtieE227Ck7gm5fmJV0=; b=etHxVxVUcaoLcPQicB6sK6mWaqb0nwSXjXswVUzombJnOuXNJu90AzTpgvWAooW0FH WGoob4IxXvTtjMTcYrwkDyLMrIBbIRQXAyJwEOtCCrhEkcLTEEII7oUyviIJNp2RdD9J mC2x0p6km+ryvh05ORW8V4BQF0m7og/ohPbWVUehfITTSQMIJD4Sxfk2Pe+iuwRsKwbl GgWngth9sRXQPspxTNMzecrF/7jeZR+kbrqaedoMtyLvybeue0M7eFZw+VCP/CY62DFl IsTFOIAMykb4mpjaBnIJ88588LdBuTk+TzewUjk+6hBJylff3xGU5H6LhUSp6LZUlX0O 8KXg== X-Forwarded-Encrypted: i=1; AJvYcCXrG6YdVIDFJ/xv/w0ClD8vMJIp+LvlflJN/eKBJIcpoOKi6DjhkKiMRei0eb5OmZ4Wt+Bgm5VvQYYZCTI=@vger.kernel.org X-Gm-Message-State: AOJu0Ywth89kAUf9vSLmVtaoK8J8agqCStfz6PUOAN27L8O5gnNMXlLk Jua8WWUhrvva3Fj4oKo0M2PyAEtn0ieKsiSasrfoe6rnbAj8EKaknVcHmWF3eDsabPiXsLXlxl4 vba0COIKOVlP72a/z8XVwEJUJhgVPAx94ORRNMkx7cuPQLarUsdwFd3Abwb4DwA== X-Gm-Gg: ASbGncvU1gS8Ifd9IcUENgLKNXyj/ZMaaaW6gvq1H6XYddXXzkoXSS2eUVQUh9Rs+DY 4s5kv+XVqctjsCOluiAWvcAFEh3GyWmCi/2IAQ0UaRk7HybCDUvCrjlESNR+2JbU1ERFSk8WKAV xzvX2ukz6y0cARxZm4o0Cc6M+3HwIXqgRr2vPl6lcgxT1J7/8D5t5mPtMj9XbCsifX8nHGBkadv d/ApMEaYbKNC3C1gktynEdqkbiEoCiN5VyBMQH7R1yAirNR15FM12m97oWLtyRP6mT+7PvMtw5u GUQ9PFuuSAi+8PJlyBWKlXDzCVQblf+15j/K0lddcKFva/ANiUbSKnS+Tm5teGha8xsqHTtIi1q l5Q0z5eU2FjUaOUhTTTl4f9Wa31KdAw== X-Received: by 2002:a05:600c:5124:b0:434:f9ad:7222 with SMTP id 5b1f17b1804b1-4396ec31d4amr87218165e9.7.1739802626798; Mon, 17 Feb 2025 06:30:26 -0800 (PST) X-Google-Smtp-Source: AGHT+IHBuJdRX9HJWRT+6db3iV86k8EuFY+S3+GwbF5Y1fECsH+Mh1mHoyPVYo4RmvcbtrSvtMMq3Q== X-Received: by 2002:a05:600c:5124:b0:434:f9ad:7222 with SMTP id 5b1f17b1804b1-4396ec31d4amr87217745e9.7.1739802626429; Mon, 17 Feb 2025 06:30:26 -0800 (PST) Received: from ?IPV6:2003:cb:c739:900:900f:3c9e:2f7b:5d0a? (p200300cbc7390900900f3c9e2f7b5d0a.dip0.t-ipconnect.de. [2003:cb:c739:900:900f:3c9e:2f7b:5d0a]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4395a04f208sm153583685e9.6.2025.02.17.06.30.23 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 17 Feb 2025 06:30:25 -0800 (PST) Message-ID: <871c0dae-c419-4ac2-9472-6901aab90dcf@redhat.com> Date: Mon, 17 Feb 2025 15:30:23 +0100 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 v7] arm64: mm: Populate vmemmap at the page level if not section aligned To: Zhenhua Huang , anshuman.khandual@arm.com, catalin.marinas@arm.com Cc: will@kernel.org, ardb@kernel.org, ryan.roberts@arm.com, mark.rutland@arm.com, joey.gouly@arm.com, dave.hansen@linux.intel.com, akpm@linux-foundation.org, chenfeiyang@loongson.cn, chenhuacai@kernel.org, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, quic_tingweiz@quicinc.com References: <20250217092907.3474806-1-quic_zhenhuah@quicinc.com> <8c1578ed-cfef-4fba-a334-ebf5eac26d60@redhat.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 17.02.25 11:34, Zhenhua Huang wrote: > > > On 2025/2/17 17:44, David Hildenbrand wrote: >> On 17.02.25 10:29, Zhenhua Huang wrote: >>> On the arm64 platform with 4K base page config, SECTION_SIZE_BITS is set >>> to 27, making one section 128M. The related page struct which vmemmap >>> points to is 2M then. >>> Commit c1cc1552616d ("arm64: MMU initialisation") optimizes the >>> vmemmap to populate at the PMD section level which was suitable >>> initially since hot plug granule is always one section(128M). However, >>> commit ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug") >>> introduced a 2M(SUBSECTION_SIZE) hot plug granule, which disrupted the >>> existing arm64 assumptions. >>> >>> The first problem is that if start or end is not aligned to a section >>> boundary, such as when a subsection is hot added, populating the entire >>> section is wasteful. >>> >>> The Next problem is if we hotplug something that spans part of 128 MiB >>> section (subsections, let's call it memblock1), and then hotplug >>> something >>> that spans another part of a 128 MiB section(subsections, let's call it >>> memblock2), and subsequently unplug memblock1, vmemmap_free() will clear >>> the entire PMD entry which also supports memblock2 even though memblock2 >>> is still active. >>> >>> Assuming hotplug/unplug sizes are guaranteed to be symmetric. Do the >>> fix similar to x86-64: populate to pages levels if start/end is not >>> aligned >>> with section boundary. >>> >>> Signed-off-by: Zhenhua Huang >>> --- >>>   arch/arm64/mm/mmu.c | 3 ++- >>>   1 file changed, 2 insertions(+), 1 deletion(-) >>> >>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c >>> index b4df5bc5b1b8..eec1666da368 100644 >>> --- a/arch/arm64/mm/mmu.c >>> +++ b/arch/arm64/mm/mmu.c >>> @@ -1178,7 +1178,8 @@ int __meminit vmemmap_populate(unsigned long >>> start, unsigned long end, int node, >>>   { >>>       WARN_ON((start < VMEMMAP_START) || (end > VMEMMAP_END)); >>> -    if (!IS_ENABLED(CONFIG_ARM64_4K_PAGES)) >>> +    if (!IS_ENABLED(CONFIG_ARM64_4K_PAGES) || >>> +        (end - start < PAGES_PER_SECTION * sizeof(struct page))) >>>           return vmemmap_populate_basepages(start, end, node, altmap); >>>       else >>>           return vmemmap_populate_hugepages(start, end, node, altmap); >> >> Yes, this does mimic what x86 does. That handling does look weird, >> because it >> doesn't care about any address alignments, only about the size, which is >> odd. >> >> I wonder if we could do better and move this handling >> into vmemmap_populate_hugepages(), where we already have a fallback >> to vmemmap_populate_basepages(). > > Hi David, > > I had the same doubt initially. > After going through the codes, I noticed for vmemmap_populate(), the > arguments "start" and "end" passed down should already be within one > section. > early path: > for_each_present_section_nr > __populate_section_memmap > .. > vmemmap_populate() > > hotplug path: > __add_pages > section_activate > vmemmap_populate() > > Therefore.. focusing only on the size seems OK to me, and fall back > solution below appears unnecessary? Ah, in that case it is fine. Might make sense to document/enforce that somehow for the time being ... >> +/* >> + * Try to populate PMDs, but fallback to populating base pages when ranges >> + * would only partially cover a PMD. >> + */ >>  int __meminit vmemmap_populate_hugepages(unsigned long start, unsigned >> long end, >>                                          int node, struct vmem_altmap >> *altmap) >>  { >> @@ -313,6 +317,9 @@ int __meminit vmemmap_populate_hugepages(unsigned >> long start, unsigned long end, >>         for (addr = start; addr < end; addr = next) { > > This for loop appears to be redundant for arm64 as well, as above > mentioned, a single call to pmd_addr_end() should suffice. Right, that was what was confusing me in the first place. > >>                 next = pmd_addr_end(addr, end); >> >> +               if (!IS_ALIGNED(addr, PMD_SIZE) || !IS_ALIGNED(next, >> PMD_SIZE)) >> +                       goto fallback; >> + >>                 pgd = vmemmap_pgd_populate(addr, node); >>                 if (!pgd) >>                         return -ENOMEM; >> @@ -346,6 +353,7 @@ int __meminit vmemmap_populate_hugepages(unsigned >> long start, unsigned long end, >>                         } >>                 } else if (vmemmap_check_pmd(pmd, node, addr, next)) >>                         continue; >> +fallback: >>                 if (vmemmap_populate_basepages(addr, next, node, altmap)) >>                         return -ENOMEM; > > It seems we have no chance to call populate_basepages here? Can you elaborate? -- Cheers, David / dhildenb