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Thu, 9 Jan 2025 09:38:57 GMT Received: from ap-kernel-sh01-lnx.qualcomm.com (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; Thu, 9 Jan 2025 01:38:53 -0800 From: Zhenhua Huang To: , CC: , , , , , , , , , , , , , Zhenhua Huang , Subject: [PATCH v5] arm64: mm: Populate vmemmap/linear at the page level for hotplugged sections Date: Thu, 9 Jan 2025 17:38:24 +0800 Message-ID: <20250109093824.452925-1-quic_zhenhuah@quicinc.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 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-Proofpoint-ORIG-GUID: S3IhCfqFeNehZ13-5ojzVPxUNz5mSdpz X-Proofpoint-GUID: S3IhCfqFeNehZ13-5ojzVPxUNz5mSdpz X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1039,Hydra:6.0.680,FMLib:17.12.60.29 definitions=2024-09-06_09,2024-09-06_01,2024-09-02_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 mlxscore=0 malwarescore=0 mlxlogscore=999 spamscore=0 impostorscore=0 priorityscore=1501 clxscore=1015 adultscore=0 phishscore=0 bulkscore=0 lowpriorityscore=0 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.19.0-2411120000 definitions=main-2501090077 X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 827E040004 X-Stat-Signature: eaj9xfczzo7m4c7hn4kk9hftzej4jw54 X-Rspam-User: X-HE-Tag: 1736415544-100052 X-HE-Meta: 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 +IvkuGwn Xl05SFG02ofwVHVzph0Ze27Fzq+niKg2QJ2NfkbggQWAx3M7R5wjFzFir0SwLU6waxTUUO1/3GFb4RGrZ5WSU0VZCfYJVPlWUHuqfjozFLwUB080DD3vT0J+3i91OdG0QZntzUkkDwlFauGEPgKAmoLVbPAAnQLmUgOi/ONRrC5QcxzL/nTVDuJ1I7xAYaUsqcpIguOnfc+nsisKRrgWcbtiZJC80lwmmLOY1lQbyI5nvnVgI8S6tPvP9RpTT7zhLrhMsFxDIo2eRs2ULBW+9NghbNvwyRq5dgeEnSxR3u93ihul9b0povPVvFTg2cD7Utb+EFQ0vAMgE1Xbhflfs50ao9g== 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 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;