From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 467B8C433F5 for ; Mon, 18 Apr 2022 15:54:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1346037AbiDRP5Q (ORCPT ); Mon, 18 Apr 2022 11:57:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54266 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345981AbiDRP5F (ORCPT ); Mon, 18 Apr 2022 11:57:05 -0400 Received: from szxga02-in.huawei.com (szxga02-in.huawei.com [45.249.212.188]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id CD57B381B2 for ; Mon, 18 Apr 2022 08:47:38 -0700 (PDT) Received: from kwepemi500016.china.huawei.com (unknown [172.30.72.56]) by szxga02-in.huawei.com (SkyGuard) with ESMTP id 4Khrq65jkxzFq1Y; Mon, 18 Apr 2022 23:45:06 +0800 (CST) Received: from kwepemm600017.china.huawei.com (7.193.23.234) by kwepemi500016.china.huawei.com (7.221.188.220) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Mon, 18 Apr 2022 23:47:36 +0800 Received: from [10.174.179.234] (10.174.179.234) by kwepemm600017.china.huawei.com (7.193.23.234) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Mon, 18 Apr 2022 23:47:34 +0800 Message-ID: Date: Mon, 18 Apr 2022 23:47:34 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Subject: Re: [PATCH -next v4 3/4] arm64: mm: add support for page table check To: Anshuman Khandual , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , , "H. Peter Anvin" , Pasha Tatashin , Andrew Morton , Catalin Marinas , Will Deacon , Paul Walmsley , Palmer Dabbelt , Albert Ou CC: , , , , Kefeng Wang , Guohanjun References: <20220418034444.520928-1-tongtiangen@huawei.com> <20220418034444.520928-4-tongtiangen@huawei.com> <1c314feb-cd78-2bb3-462e-4ea3cefe122e@arm.com> From: Tong Tiangen In-Reply-To: <1c314feb-cd78-2bb3-462e-4ea3cefe122e@arm.com> Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.179.234] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To kwepemm600017.china.huawei.com (7.193.23.234) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2022/4/18 17:28, Anshuman Khandual 写道: > On 4/18/22 09:14, Tong Tiangen wrote: >> From: Kefeng Wang >> [...] >> #endif > > Ran this series on arm64 platform after enabling > > - CONFIG_PAGE_TABLE_CHECK > - CONFIG_PAGE_TABLE_CHECK_ENFORCED (avoiding kernel command line option) > > After some time, the following error came up > > [ 23.266013] ------------[ cut here ]------------ > [ 23.266807] kernel BUG at mm/page_table_check.c:90! > [ 23.267609] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP > [ 23.268503] Modules linked in: > [ 23.269012] CPU: 1 PID: 30 Comm: khugepaged Not tainted 5.18.0-rc3-00004-g60aa8e363a91 #2 > [ 23.270383] Hardware name: linux,dummy-virt (DT) > [ 23.271210] pstate: 40400005 (nZcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) > [ 23.272445] pc : page_table_check_clear.isra.6+0x114/0x148 > [ 23.273429] lr : page_table_check_clear.isra.6+0x64/0x148 > [ 23.274395] sp : ffff80000afb3ca0 > [ 23.274994] x29: ffff80000afb3ca0 x28: fffffc00022558e8 x27: ffff80000a27f628 > [ 23.276260] x26: ffff800009f9f2b0 x25: ffff00008a8d5000 x24: ffff800009f09fa0 > [ 23.277527] x23: 0000ffff89e00000 x22: ffff800009f09fb8 x21: ffff000089414cc0 > [ 23.278798] x20: 0000000000000200 x19: fffffc00022a0000 x18: 0000000000000001 > [ 23.280066] x17: 0000000000000001 x16: 0000000000000000 x15: 0000000000000003 > [ 23.281331] x14: 0000000000000068 x13: 00000000000000c0 x12: 0000000000000010 > [ 23.282602] x11: fffffc0002320008 x10: fffffc0002320000 x9 : ffff800009fa1000 > [ 23.283868] x8 : 00000000ffffffff x7 : 0000000000000001 x6 : ffff800009fa1f08 > [ 23.285135] x5 : 0000000000000000 x4 : 0000000000000000 x3 : 0000000000000000 > [ 23.286406] x2 : 00000000ffffffff x1 : ffff000080f2800c x0 : ffff000080f28000 > [ 23.287673] Call trace: > [ 23.288123] page_table_check_clear.isra.6+0x114/0x148 > [ 23.289043] __page_table_check_pmd_clear+0x3c/0x50 > [ 23.289918] pmdp_collapse_flush+0x114/0x370 > [ 23.290692] khugepaged+0x1170/0x19e0 > [ 23.291356] kthread+0x110/0x120 > [ 23.291945] ret_from_fork+0x10/0x20 > [ 23.292596] Code: 91001041 b8e80024 51000482 36fffd62 (d4210000) > [ 23.293678] ---[ end trace 0000000000000000 ]--- > [ 23.294511] note: khugepaged[30] exited with preempt_count 2 > > Looking into file mm/page_table_check.c where this problem occured. > > /* > * An enty is removed from the page table, decrement the counters for that page > * verify that it is of correct type and counters do not become negative. > */ > static void page_table_check_clear(struct mm_struct *mm, unsigned long addr, > unsigned long pfn, unsigned long pgcnt) > { > struct page_ext *page_ext; > struct page *page; > unsigned long i; > bool anon; > > if (!pfn_valid(pfn)) > return; > > page = pfn_to_page(pfn); > page_ext = lookup_page_ext(page); > anon = PageAnon(page); > > for (i = 0; i < pgcnt; i++) { > struct page_table_check *ptc = get_page_table_check(page_ext); > > if (anon) { > BUG_ON(atomic_read(&ptc->file_map_count)); > BUG_ON(atomic_dec_return(&ptc->anon_map_count) < 0); > } else { > BUG_ON(atomic_read(&ptc->anon_map_count)); > Triggered here ====>> BUG_ON(atomic_dec_return(&ptc->file_map_count) < 0); > } > page_ext = page_ext_next(page_ext); > } > } > > Could you explain what was expected during pmdp_collapse_flush() which when > failed, triggered this BUG_ON() ? This counter seems to be page table check > specific, could it just go wrong ? I have not looked into the details about > page table check mechanism. > > - Anshuman > . Hi Anshuman: Thanks for your job. Let me briefly explain the principle of page table check(PTC). PTC introduces the following struct for page mapping type count: struct page_table_check { atomic_t anon_map_count; atomic_t file_map_count; }; This structure can be obtained by "lookup_page_ext(page)" When page table entries are set(pud/pmd/pte), page_table_check_set() is called to increase the page mapping count, Also check for errors (eg:if a page is used for anonymous mapping, then the page cannot be used for file mapping at the same time). When page table entries are clear(pud/pmd/pte), page_table_check_clear() is called to decrease the page mapping count, Also check for errors. The error check rules are described in the following documents: Documentation/vm/page_table_check.rst The setting and clearing of page table entries are symmetrical. Here __page_table_check_pmd_clear() trigger BUGON which indicates that the pmd entry file mapping count has become negative. I guess if PTC didn't detect this exception, would there have been any problems? Thanks, Tong. 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Peter Anvin" , Pasha Tatashin , Andrew Morton , Catalin Marinas , Will Deacon , Paul Walmsley , Palmer Dabbelt , Albert Ou CC: , , , , Kefeng Wang , Guohanjun References: <20220418034444.520928-1-tongtiangen@huawei.com> <20220418034444.520928-4-tongtiangen@huawei.com> <1c314feb-cd78-2bb3-462e-4ea3cefe122e@arm.com> From: Tong Tiangen In-Reply-To: <1c314feb-cd78-2bb3-462e-4ea3cefe122e@arm.com> X-Originating-IP: [10.174.179.234] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To kwepemm600017.china.huawei.com (7.193.23.234) X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220418_084744_939654_9D0F6E76 X-CRM114-Status: GOOD ( 18.32 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: base64 Content-Type: text/plain; charset="utf-8"; Format="flowed" 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(7.193.23.234) by kwepemi500016.china.huawei.com (7.221.188.220) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Mon, 18 Apr 2022 23:47:36 +0800 Received: from [10.174.179.234] (10.174.179.234) by kwepemm600017.china.huawei.com (7.193.23.234) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Mon, 18 Apr 2022 23:47:34 +0800 Message-ID: Date: Mon, 18 Apr 2022 23:47:34 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Subject: Re: [PATCH -next v4 3/4] arm64: mm: add support for page table check To: Anshuman Khandual , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , , "H. Peter Anvin" , Pasha Tatashin , Andrew Morton , Catalin Marinas , Will Deacon , Paul Walmsley , Palmer Dabbelt , Albert Ou CC: , , , , Kefeng Wang , Guohanjun References: <20220418034444.520928-1-tongtiangen@huawei.com> <20220418034444.520928-4-tongtiangen@huawei.com> <1c314feb-cd78-2bb3-462e-4ea3cefe122e@arm.com> From: Tong Tiangen In-Reply-To: <1c314feb-cd78-2bb3-462e-4ea3cefe122e@arm.com> X-Originating-IP: [10.174.179.234] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To kwepemm600017.china.huawei.com (7.193.23.234) X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20220418_084744_939654_9D0F6E76 X-CRM114-Status: GOOD ( 18.32 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Transfer-Encoding: base64 Content-Type: text/plain; charset="utf-8"; Format="flowed" 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