From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mx0a-0031df01.pphosted.com (mx0a-0031df01.pphosted.com [205.220.168.131]) (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 8DAEABE6C; Wed, 15 Jan 2025 02:14:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=205.220.168.131 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736907247; cv=none; b=ba3ddE4S3C0/NTx93NzwfNGv4QKgptNxebI2/2EhzrYrihw5y49eRtJ/MGYohRjgO3j6CGmpKGR0KH8e6M4MQyWpm8Ma0jGx7I4graMy5BWzXN01TuTreLLvHWdtPGk32Nx6ypn+YsIhj87Hb/yp9Pr0fyE7PHPwz7W3wq3dZGw= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1736907247; c=relaxed/simple; bh=kWeRQdyat6TiZOrY10DmCqvzZNoQtHCcR9ebQNu0lVI=; h=Message-ID:Date:MIME-Version:Subject:To:CC:References:From: In-Reply-To:Content-Type; b=HQP/UZlws+ykbLMWxbAkKcTuJJgwdENLmY1a4fGckV8Avynf729mJRPjQToBCjDmYR+0pB/YmvjHvfxs8FXbyg+z6aBWWbOGzvtDWv+1W3sPwtV2/6OZ6gqsGvQVq2Y1l6zOe+v0pGoPgALfanfRXKeN4AHMmQfh6f45ngi22XM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=quicinc.com; spf=pass smtp.mailfrom=quicinc.com; dkim=pass (2048-bit key) header.d=quicinc.com header.i=@quicinc.com header.b=lALW9OYt; arc=none smtp.client-ip=205.220.168.131 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=quicinc.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=quicinc.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=quicinc.com header.i=@quicinc.com header.b="lALW9OYt" Received: from pps.filterd (m0279862.ppops.net [127.0.0.1]) by mx0a-0031df01.pphosted.com (8.18.1.2/8.18.1.2) with ESMTP id 50EBEY3T000879; Wed, 15 Jan 2025 02:13:34 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=quicinc.com; h= cc:content-transfer-encoding:content-type:date:from:in-reply-to :message-id:mime-version:references:subject:to; s=qcppdkim1; bh= 1+eUp8lGe+ej895FJwwzd/ghRECdXZi8mrUuHFzRS3Q=; b=lALW9OYt/Djbf7wz bG4qGyG2+OK6615H0gsfXe1ZGrN5VAHEBqERcUKiLWLg+Pt1+v62jpPyNjbJC4yP uvBLfSE4WC2jh+ot/5ZHBwU8dIPZeKvwbdkUTp12Iy73dUj9uB4DEX0wfoP8is0Z iRyUxNX5VHA+LAFaTXCDIKBlFNeFytedlE8UnMlCt06nz/+YXtbLQWreQaYQ5DC+ /5DQeMsiYYe778p/RPpIGYQnxs3NXcfc1Mf9xqu8D68PshRAgSQhhNJ2UH1Fq5t6 CEJu4mARmWZqgklBqyuCFmyyQKY+pzDsxfxpbEBk5GTuX3Fvd4Y6IFP5WsEQrlG8 Q4KJew== Received: from nalasppmta03.qualcomm.com (Global_NAT1.qualcomm.com [129.46.96.20]) by mx0a-0031df01.pphosted.com (PPS) with ESMTPS id 445pvnsugm-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 15 Jan 2025 02:13:33 +0000 (GMT) Received: from nalasex01a.na.qualcomm.com (nalasex01a.na.qualcomm.com [10.47.209.196]) by NALASPPMTA03.qualcomm.com (8.18.1.2/8.18.1.2) with ESMTPS id 50F2DXhG003342 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 15 Jan 2025 02:13:33 GMT Received: from [10.239.132.245] (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; Tue, 14 Jan 2025 18:13:28 -0800 Message-ID: <9ae36424-2cb6-491d-8ac2-95bfe39828a2@quicinc.com> Date: Wed, 15 Jan 2025 10:13:21 +0800 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 v5] arm64: mm: Populate vmemmap/linear at the page level for hotplugged sections To: , CC: , , , , , , , , , , , , , References: <20250109093824.452925-1-quic_zhenhuah@quicinc.com> Content-Language: en-US From: Zhenhua Huang In-Reply-To: <20250109093824.452925-1-quic_zhenhuah@quicinc.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 7bit 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-Proofpoint-GUID: YZhbkYNUb3w3w3vxjGdgWjHV3gLmQkpJ X-Proofpoint-ORIG-GUID: YZhbkYNUb3w3w3vxjGdgWjHV3gLmQkpJ X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1057,Hydra:6.0.680,FMLib:17.12.68.34 definitions=2025-01-14_09,2025-01-13_02,2024-11-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 adultscore=0 clxscore=1015 priorityscore=1501 lowpriorityscore=0 phishscore=0 bulkscore=0 mlxscore=0 malwarescore=0 suspectscore=0 spamscore=0 mlxlogscore=999 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2411120000 definitions=main-2501150013 Gentle reminder if you happened to miss it :) On 2025/1/9 17:38, 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. > > Considering the vmemmap_free -> unmap_hotplug_pmd_range path, when > pmd_sect() is true, the entire PMD section is cleared, even if there is > other effective subsection. For example page_struct_map1 and > page_strcut_map2 are part of a single PMD entry and they are hot-added > sequentially. Then page_struct_map1 is removed, vmemmap_free() will clear > the entire PMD entry freeing the struct page map for the whole section, > even though page_struct_map2 is still active. Similar problem exists > with linear mapping as well, for 16K base page(PMD size = 32M) or 64K > base page(PMD = 512M), their block mappings exceed SUBSECTION_SIZE. > Tearing down the entire PMD mapping too will leave other subsections > unmapped in the linear mapping. > > To address the issue, we need to prevent PMD/PUD/CONT mappings for both > linear and vmemmap for non-boot sections if corresponding size on the > given base page exceeds SUBSECTION_SIZE(2MB now). > > Cc: stable@vger.kernel.org # v5.4+ > Fixes: ba72b4c8cf60 ("mm/sparsemem: support sub-section hotplug") > Signed-off-by: Zhenhua Huang > --- > Hi Catalin and Anshuman, > I have addressed comments so far, please help review. > One outstanding point which not finalized is in vmemmap_populate(): how to judge hotplug > section. Currently I am using system_state, discussion: > https://lore.kernel.org/linux-mm/1515dae4-cb53-4645-8c72-d33b27ede7eb@quicinc.com/ > arch/arm64/mm/mmu.c | 46 ++++++++++++++++++++++++++++++++++++--------- > 1 file changed, 37 insertions(+), 9 deletions(-) > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index e2739b69e11b..8718d6e454c5 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -42,9 +42,13 @@ > #include > #include > > -#define NO_BLOCK_MAPPINGS BIT(0) > -#define NO_CONT_MAPPINGS BIT(1) > -#define NO_EXEC_MAPPINGS BIT(2) /* assumes FEAT_HPDS is not used */ > +#define NO_PMD_BLOCK_MAPPINGS BIT(0) > +#define NO_PUD_BLOCK_MAPPINGS BIT(1) /* Hotplug case: do not want block mapping for PUD */ > +#define NO_BLOCK_MAPPINGS (NO_PMD_BLOCK_MAPPINGS | NO_PUD_BLOCK_MAPPINGS) > +#define NO_PTE_CONT_MAPPINGS BIT(2) > +#define NO_PMD_CONT_MAPPINGS BIT(3) /* Hotplug case: do not want cont mapping for PMD */ > +#define NO_CONT_MAPPINGS (NO_PTE_CONT_MAPPINGS | NO_PMD_CONT_MAPPINGS) > +#define NO_EXEC_MAPPINGS BIT(4) /* assumes FEAT_HPDS is not used */ > > u64 kimage_voffset __ro_after_init; > EXPORT_SYMBOL(kimage_voffset); > @@ -224,7 +228,7 @@ static void alloc_init_cont_pte(pmd_t *pmdp, unsigned long addr, > > /* use a contiguous mapping if the range is suitably aligned */ > if ((((addr | next | phys) & ~CONT_PTE_MASK) == 0) && > - (flags & NO_CONT_MAPPINGS) == 0) > + (flags & NO_PTE_CONT_MAPPINGS) == 0) > __prot = __pgprot(pgprot_val(prot) | PTE_CONT); > > init_pte(ptep, addr, next, phys, __prot); > @@ -254,7 +258,7 @@ static void init_pmd(pmd_t *pmdp, unsigned long addr, unsigned long end, > > /* try section mapping first */ > if (((addr | next | phys) & ~PMD_MASK) == 0 && > - (flags & NO_BLOCK_MAPPINGS) == 0) { > + (flags & NO_PMD_BLOCK_MAPPINGS) == 0) { > pmd_set_huge(pmdp, phys, prot); > > /* > @@ -311,7 +315,7 @@ static void alloc_init_cont_pmd(pud_t *pudp, unsigned long addr, > > /* use a contiguous mapping if the range is suitably aligned */ > if ((((addr | next | phys) & ~CONT_PMD_MASK) == 0) && > - (flags & NO_CONT_MAPPINGS) == 0) > + (flags & NO_PMD_CONT_MAPPINGS) == 0) > __prot = __pgprot(pgprot_val(prot) | PTE_CONT); > > init_pmd(pmdp, addr, next, phys, __prot, pgtable_alloc, flags); > @@ -358,8 +362,8 @@ static void alloc_init_pud(p4d_t *p4dp, unsigned long addr, unsigned long end, > * For 4K granule only, attempt to put down a 1GB block > */ > if (pud_sect_supported() && > - ((addr | next | phys) & ~PUD_MASK) == 0 && > - (flags & NO_BLOCK_MAPPINGS) == 0) { > + ((addr | next | phys) & ~PUD_MASK) == 0 && > + (flags & NO_PUD_BLOCK_MAPPINGS) == 0) { > pud_set_huge(pudp, phys, prot); > > /* > @@ -1177,7 +1181,13 @@ 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)) > + /* > + * Hotplugged section does not support hugepages as > + * PMD_SIZE (hence PUD_SIZE) section mapping covers > + * struct page range that exceeds a SUBSECTION_SIZE > + * i.e 2MB - for all available base page sizes. > + */ > + if (!IS_ENABLED(CONFIG_ARM64_4K_PAGES) || system_state != SYSTEM_BOOTING) > return vmemmap_populate_basepages(start, end, node, altmap); > else > return vmemmap_populate_hugepages(start, end, node, altmap); > @@ -1339,9 +1349,27 @@ int arch_add_memory(int nid, u64 start, u64 size, > struct mhp_params *params) > { > int ret, flags = NO_EXEC_MAPPINGS; > + unsigned long start_pfn = PFN_DOWN(start); > + struct mem_section *ms = __pfn_to_section(start_pfn); > > VM_BUG_ON(!mhp_range_allowed(start, size, true)); > > + /* should not be invoked by early section */ > + WARN_ON(early_section(ms)); > + > + /* > + * Disallow BlOCK/CONT mappings if the corresponding size exceeds > + * SUBSECTION_SIZE which now is 2MB. > + * > + * PUD_BLOCK or PMD_CONT should consistently exceed SUBSECTION_SIZE > + * across all variable page size configurations, so add them directly > + */ > + flags |= NO_PUD_BLOCK_MAPPINGS | NO_PMD_CONT_MAPPINGS; > + if (SUBSECTION_SHIFT < PMD_SHIFT) > + flags |= NO_PMD_BLOCK_MAPPINGS; > + if (SUBSECTION_SHIFT < CONT_PTE_SHIFT) > + flags |= NO_PTE_CONT_MAPPINGS; > + > if (can_set_direct_map()) > flags |= NO_BLOCK_MAPPINGS | NO_CONT_MAPPINGS; >