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Tue, 4 Mar 2025 07:26:03 GMT Received: from [10.253.15.36] (10.80.80.8) by nalasex01a.na.qualcomm.com (10.47.209.196) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.1544.9; Mon, 3 Mar 2025 23:25:58 -0800 Message-ID: Date: Tue, 4 Mar 2025 15:25:55 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8] arm64: mm: Populate vmemmap at the page level if not section aligned To: David Hildenbrand , , CC: , , , , , , , , , , , , , References: <20250219084001.1272445-1-quic_zhenhuah@quicinc.com> <78d55e35-6cda-4f5e-8e52-0a54b1e64592@redhat.com> Content-Language: en-US From: Zhenhua Huang In-Reply-To: <78d55e35-6cda-4f5e-8e52-0a54b1e64592@redhat.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.80.80.8] X-ClientProxiedBy: nasanex01b.na.qualcomm.com (10.46.141.250) To nalasex01a.na.qualcomm.com (10.47.209.196) X-QCInternal: smtphost X-Proofpoint-Virus-Version: vendor=nai engine=6200 definitions=5800 signatures=585085 X-Authority-Analysis: v=2.4 cv=PMb1+eqC c=1 sm=1 tr=0 ts=67c6ab0b cx=c_pps a=ouPCqIW2jiPt+lZRy3xVPw==:117 a=ouPCqIW2jiPt+lZRy3xVPw==:17 a=GEpy-HfZoHoA:10 a=IkcTkHD0fZMA:10 a=Vs1iUdzkB0EA:10 a=VwQbUJbxAAAA:8 a=COk6AnOGAAAA:8 a=20KFwNOVAAAA:8 a=OyIDkqIgn3q2G5mQ1iQA:9 a=3ZKOabzyN94A:10 a=QEXdDO2ut3YA:10 a=TjNXssC_j7lpFel5tvFf:22 X-Proofpoint-ORIG-GUID: qN3xRsxJfR6rENMgdFiS9cnF5DmYD864 X-Proofpoint-GUID: qN3xRsxJfR6rENMgdFiS9cnF5DmYD864 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1093,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-03-04_03,2025-03-03_04,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 bulkscore=0 mlxlogscore=999 phishscore=0 lowpriorityscore=0 malwarescore=0 priorityscore=1501 mlxscore=0 adultscore=0 spamscore=0 suspectscore=0 impostorscore=0 clxscore=1015 classifier=spam authscore=0 adjust=0 reason=mlx scancount=1 engine=8.19.0-2502100000 definitions=main-2503040061 X-Rspam-User: X-Stat-Signature: c5qwu51f4j9nkw7zrkmxftm7o6m5rit4 X-Rspamd-Queue-Id: 74D141C000D X-Rspamd-Server: rspam07 X-HE-Tag: 1741073173-364042 X-HE-Meta: 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 QyZXMs+1 kEmzxfJ9ovef4hJyjxgTj7mQtasUqiQ1paBpdGLPAGcvMSMUf4IBfJQcuO9gxW/Vdd8aj1qtPGNC0jZgDPpnKEG9yoyzNQ7DXgjshsHUYyvab9mVca4kngsUhhcvVuINCCOviTPGKA1bpABiLK+D9jvfRn0UnQZXMslmnycTB8dMWL9eBIo/C6bMALr/MWYpzbYiXJzQlp5brqeheRNcGcwsHMIs3hz0VmzuYa5dTRYMoW3dkJ9Xqr8GHeEOGeMVXyiZ6zjqdJ+xmtdkB0pHqpT5lfzdg6jy8TGj3vm/lbc3ZNKmp6+IMyDiBFczPePhRcagmtfyAMI+qLOESG8e7lK1daCMrB/6fCMAZid7cYGCVEhP15S8wV/h9rPI8OEB6dwUuHIEWJsJWwiHbd9xcYLoIzuFy357wVyKeXe8bAIKm70OQLCHVdy30jg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 2025/3/3 18:01, David Hildenbrand wrote: > On 19.02.25 09:40, 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. >> >> Cc: # v5.4+ >> Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug") >> Signed-off-by: Zhenhua Huang >> --- >> Hi Catalin and David, >> Following our latest discussion, I've updated the patch for your review. >> I also removed Catalin's review tag since I've made significant >> modifications. >>   arch/arm64/mm/mmu.c | 5 ++++- >>   1 file changed, 4 insertions(+), 1 deletion(-) >> >> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c >> index b4df5bc5b1b8..de05ccf47f21 100644 >> --- a/arch/arm64/mm/mmu.c >> +++ b/arch/arm64/mm/mmu.c >> @@ -1177,8 +1177,11 @@ int __meminit vmemmap_populate(unsigned long >> start, unsigned long end, int node, >>           struct vmem_altmap *altmap) >>   { >>       WARN_ON((start < VMEMMAP_START) || (end > VMEMMAP_END)); >> +    /* [start, end] should be within one section */ >> +    WARN_ON(end - start > PAGES_PER_SECTION * sizeof(struct page)); >> -    if (!IS_ENABLED(CONFIG_ARM64_4K_PAGES)) >> +    if (!IS_ENABLED(CONFIG_ARM64_4K_PAGES) || >> +        (end - start < PAGES_PER_SECTION * sizeof(struct page))) > > Indentation should be > >     if (!IS_ENABLED(CONFIG_ARM64_4K_PAGES) || >         (end - start < PAGES_PER_SECTION * sizeof(struct page))) > Thanks, I will repost with the above fix and WARN_ON_ONCE as you preferred in v7. > > Acked-by: David Hildenbrand > > > Thanks! >