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[2620:137:e000::1:20]) by mx.google.com with ESMTP id t14-20020a05640203ce00b005219817ce6asi818194edw.676.2023.07.17.05.23.35; Mon, 17 Jul 2023 05:23:59 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; Authentication-Results: mx.google.com; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=QUARANTINE sp=QUARANTINE dis=NONE) header.from=huawei.com Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230017AbjGQLwB (ORCPT + 99 others); Mon, 17 Jul 2023 07:52:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58944 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229564AbjGQLwA (ORCPT ); Mon, 17 Jul 2023 07:52:00 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 884B597 for ; Mon, 17 Jul 2023 04:51:57 -0700 (PDT) Received: from dggpemm500014.china.huawei.com (unknown [172.30.72.55]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4R4L5F6xJDz18LlC; Mon, 17 Jul 2023 19:51:13 +0800 (CST) Received: from localhost.localdomain (10.175.112.125) by dggpemm500014.china.huawei.com (7.185.36.153) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.27; Mon, 17 Jul 2023 19:51:54 +0800 From: Wupeng Ma To: , , CC: , , , , , , , Subject: [RFC PATCH] arm64: mm: Fix kernel page tables incorrectly deleted during memory removal Date: Mon, 17 Jul 2023 19:51:50 +0800 Message-ID: <20230717115150.1806954-1-mawupeng1@huawei.com> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-Originating-IP: [10.175.112.125] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To dggpemm500014.china.huawei.com (7.185.36.153) X-CFilter-Loop: Reflected X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_BLOCKED,RCVD_IN_MSPIKE_H5,RCVD_IN_MSPIKE_WL, SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1771670485602709147 X-GMAIL-MSGID: 1771670485602709147 From: Ma Wupeng During our test, we found that kernel page table may be unexpectedly cleared with rodata off. The root cause is that the kernel page is initialized with pud size(1G block mapping) while offline is memory block size(MIN_MEMORY_BLOCK_SIZE 128M), eg, if 2G memory is hot-added, when offline a memory block, the call trace is shown below, offline_and_remove_memory try_remove_memory arch_remove_memory __remove_pgd_mapping unmap_hotplug_range unmap_hotplug_p4d_range unmap_hotplug_pud_range if (pud_sect(pud)) pud_clear(pudp); There is no issue for block mapping with pmd level(2M) because the memory block size is aligned with 2M. Commit f0b13ee23241 ("arm64/sparsemem: reduce SECTION_SIZE_BITS") reduces SECTION_SIZE_BITS from arm64, this make memory section size less than pud size possible. Since only hotadded memory can be removed for arm64 due to commit bbd6ec605c0f ("arm64/mm: Enable memory hot remove"), stop using pud size kernel page entry during memory hot join can fix this. Fixes: f0b13ee23241 ("arm64/sparsemem: reduce SECTION_SIZE_BITS") Signed-off-by: Ma Wupeng --- arch/arm64/mm/mmu.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 95d360805f8a..44c724ce4f70 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -44,6 +44,7 @@ #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_PUD_MAPPINGS BIT(3) int idmap_t0sz __ro_after_init; @@ -344,7 +345,7 @@ static void alloc_init_pud(pgd_t *pgdp, unsigned long addr, unsigned long end, */ if (pud_sect_supported() && ((addr | next | phys) & ~PUD_MASK) == 0 && - (flags & NO_BLOCK_MAPPINGS) == 0) { + (flags & (NO_BLOCK_MAPPINGS | NO_PUD_MAPPINGS)) == 0) { pud_set_huge(pudp, phys, prot); /* @@ -1305,7 +1306,7 @@ struct range arch_get_mappable_range(void) int arch_add_memory(int nid, u64 start, u64 size, struct mhp_params *params) { - int ret, flags = NO_EXEC_MAPPINGS; + int ret, flags = NO_EXEC_MAPPINGS | NO_PUD_MAPPINGS; VM_BUG_ON(!mhp_range_allowed(start, size, true));