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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 8164CC5478C for ; Fri, 1 Mar 2024 08:54:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:From:References:Cc:To: Subject:MIME-Version:Date:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=FpCRVHgRLNuYPppLu8zC6ZfrAYiPE9YqcdCHAzAvVbI=; b=gVr3uJCNGtfLJN xsj+ONyQH5PoGYSWkuYyWSe+rtnnfD6wAhAXkns/mt4hJIf3fPG1ZGlYW+brOUb3+VSWWwnBicsrw kcddGd9u/hcRrw1fNqB9ZJf59l8Zxbb/4I5eyRNIiRudhbriVgsiG01uc04gih4F5Y2YJtV7CUhMi LWxOnyNuChMmQ9LRrwERz3f23qsz/WhMOk39kvBLMw3JbtoPk/3Ug6tcqxHdsFl/tZ1H2KDq3U2dL uEJYhl7GmKwtNeebeO/3booZekeYK0jCsqxgjZBBIkGVeHxbxVC3jn040ha9I5CjuckKFI3DB+BM5 UoMWdsfbf3wJFi9ezfdQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rfyeh-0000000H0oK-2eu5; Fri, 01 Mar 2024 08:54:11 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rfyee-0000000H0mz-1lxu for linux-arm-kernel@lists.infradead.org; Fri, 01 Mar 2024 08:54:10 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 300E21FB; Fri, 1 Mar 2024 00:54:43 -0800 (PST) Received: from [10.57.68.58] (unknown [10.57.68.58]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id BF36C3F762; Fri, 1 Mar 2024 00:54:02 -0800 (PST) Message-ID: <133a91b8-bc8b-42b3-afcd-595d7f45db84@arm.com> Date: Fri, 1 Mar 2024 08:54:00 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 36/43] arm64: mm: Add support for folding PUDs at runtime Content-Language: en-GB To: Nathan Chancellor , Matthew Wilcox Cc: Ard Biesheuvel , linux-arm-kernel@lists.infradead.org, Ard Biesheuvel , Catalin Marinas , Will Deacon , Marc Zyngier , Mark Rutland , Anshuman Khandual , Kees Cook , Aishwarya TCV , Mark Brown References: <20240214122845.2033971-45-ardb+git@google.com> <20240214122845.2033971-81-ardb+git@google.com> <20240229230159.GA1001503@dev-arch.thelio-3990X> From: Ryan Roberts In-Reply-To: <20240229230159.GA1001503@dev-arch.thelio-3990X> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240301_005408_592921_3B4927BE X-CRM114-Status: GOOD ( 26.43 ) 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-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org + Matthew On 29/02/2024 23:01, Nathan Chancellor wrote: > On Thu, Feb 29, 2024 at 02:17:52PM +0000, Ryan Roberts wrote: >> Hi Ard, >> >> On 14/02/2024 12:29, Ard Biesheuvel wrote: >>> From: Ard Biesheuvel >>> >>> In order to support LPA2 on 16k pages in a way that permits non-LPA2 >>> systems to run the same kernel image, we have to be able to fall back to >>> at most 48 bits of virtual addressing. >>> >>> Falling back to 48 bits would result in a level 0 with only 2 entries, >>> which is suboptimal in terms of TLB utilization. So instead, let's fall >>> back to 47 bits in that case. This means we need to be able to fold PUDs >>> dynamically, similar to how we fold P4Ds for 48 bit virtual addressing >>> on LPA2 with 4k pages. >> >> I'm seeing a panic during boot in today's linux-next (20240229) and bisect seems pretty confident that this commit is the offender. That said, its the merge commit that shows up as the problem commit: >> >> 26843fe8fa72 Merge branch 'for-next/core' of git://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux >> >> but when testing the arm64's for-next/core, the problem doesn't exist. So I rebased the branch into linux-next and bisected again. That time, it fingers this patch. So I guess there is some interaction between this and other changes in next? > <...> >> [ 0.161062] debug_vm_pgtable: [debug_vm_pgtable ]: Validating architecture page table helpers >> [ 0.161416] BUG: Bad page state in process swapper/0 pfn:18a65d >> [ 0.161634] page does not match folio >> [ 0.161753] page: refcount:0 mapcount:-512 mapping:0000000000000000 index:0x0 pfn:0x18a65d >> [ 0.162046] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000008 >> [ 0.162332] Mem abort info: >> [ 0.162427] ESR = 0x0000000096000004 >> [ 0.162559] EC = 0x25: DABT (current EL), IL = 32 bits >> [ 0.162723] SET = 0, FnV = 0 >> [ 0.162827] EA = 0, S1PTW = 0 >> [ 0.162933] FSC = 0x04: level 0 translation fault >> [ 0.163089] Data abort info: >> [ 0.163189] ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000 >> [ 0.163370] CM = 0, WnR = 0, TnD = 0, TagAccess = 0 >> [ 0.163539] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 >> [ 0.163719] [0000000000000008] user address but active_mm is swapper >> [ 0.163934] Internal error: Oops: 0000000096000004 [#1] PREEMPT SMP >> [ 0.164143] Modules linked in: >> [ 0.164251] CPU: 1 PID: 1 Comm: swapper/0 Not tainted 6.8.0-rc6-00966-gde701dc1f7f8 #25 >> [ 0.164516] Hardware name: linux,dummy-virt (DT) >> [ 0.164704] pstate: 21400005 (nzCv daif +PAN -UAO -TCO +DIT -SSBS BTYPE=--) >> [ 0.165052] pc : get_pfnblock_flags_mask+0x3c/0x68 >> [ 0.165281] lr : __dump_page+0x1a0/0x408 >> [ 0.165504] sp : ffff80008007b8f0 >> [ 0.165715] x29: ffff80008007b8f0 x28: 0000000000ffffc0 x27: 0000000000000000 >> [ 0.166047] x26: ffff80008007b950 x25: 0000000000000000 x24: 00000000fffffdff >> [ 0.166358] x23: ffffba8a417ba000 x22: 000000000018a65d x21: ffffba8a41601bf8 >> [ 0.166701] x20: ffff80008007b950 x19: ffff80008007b950 x18: 0000000000000006 >> [ 0.167036] x17: 78303a7865646e69 x16: 2030303030303030 x15: 0720072007200720 >> [ 0.167365] x14: 0720072007200720 x13: 0720072007200720 x12: 0720072007200720 >> [ 0.167693] x11: 0720072007200720 x10: ffffba8a4269c038 x9 : ffffba8a3fb0d0b8 >> [ 0.168017] x8 : 00000000ffffefff x7 : ffffba8a4269c038 x6 : 80000000fffff000 >> [ 0.168346] x5 : 000003fffff81de4 x4 : 0001fffffc0ef230 x3 : 0000000000000000 >> [ 0.168699] x2 : 0000000000000007 x1 : fffffe0779181ee5 x0 : 00000000001fffff >> [ 0.169041] Call trace: >> [ 0.169164] get_pfnblock_flags_mask+0x3c/0x68 >> [ 0.169413] dump_page+0x2c/0x70 >> [ 0.169565] bad_page+0x84/0x130 >> [ 0.169734] free_page_is_bad_report+0xa0/0xb8 >> [ 0.169958] free_unref_page_prepare+0x350/0x428 >> [ 0.170132] free_unref_page+0x50/0x1f0 >> [ 0.170278] __free_pages+0x11c/0x160 >> [ 0.170417] free_pages.part.0+0x6c/0x88 >> [ 0.170576] free_pages+0x1c/0x38 >> [ 0.170703] destroy_args+0x1c8/0x330 >> [ 0.170890] debug_vm_pgtable+0xae8/0x10f8 >> [ 0.171059] do_one_initcall+0x60/0x2c0 >> [ 0.171222] kernel_init_freeable+0x1ec/0x3d8 >> [ 0.171406] kernel_init+0x28/0x1f0 >> [ 0.171557] ret_from_fork+0x10/0x20 >> [ 0.171712] Code: d37b1884 f100007f 8b040064 9a831083 (f9400460) >> [ 0.171963] ---[ end trace 0000000000000000 ]--- >> [ 0.172156] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b >> [ 0.172383] SMP: stopping secondary CPUs >> [ 0.172649] Kernel Offset: 0x3a89bf800000 from 0xffff800080000000 >> [ 0.173923] PHYS_OFFSET: 0xfffff76180000000 >> [ 0.174585] CPU features: 0x0,00000000,2004454a,13867723 >> [ 0.175707] Memory Limit: none >> [ 0.176261] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b ]--- > > I did a second bisection by merging https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git for-next/stage1-lpa2 > on top of the merges before for-next/core and eventually landed on: > > d67cd9f23139ddfd7e0ef1e18474c16445188433 is the first bad commit > commit d67cd9f23139ddfd7e0ef1e18474c16445188433 > Author: Matthew Wilcox (Oracle) > Date: Tue Feb 27 19:23:31 2024 +0000 > > mm: add __dump_folio() > > Turn __dump_page() into a wrapper around __dump_folio(). Snapshot the > page & folio into a stack variable so we don't hit BUG_ON() if an > allocation is freed under us and what was a folio pointer becomes a > pointer to a tail page. > > Link: https://lkml.kernel.org/r/20240227192337.757313-5-willy@infradead.org > Signed-off-by: Matthew Wilcox (Oracle) > Signed-off-by: Andrew Morton So is that suggesting that Ard's patch is doing something that the old __dump_page() was ok with but the new version doesn't like? I don't think so, because the bad page detection has already happened before we get to __dump_page(). So I'm not really sure how this patch is involved? I'm hoping that either Ard or Matthew may be able to take a look and advise. > > mm/debug.c | 120 +++++++++++++++++++++++++++++++++---------------------------- > 1 file changed, 66 insertions(+), 54 deletions(-) > > # bad: [7f43e0f76e4710b2882c551519eff50e502115c5] Merge branch 'for-next' of git://git.kernel.org/pub/scm/linux/kernel/git/rmk/linux.git > # good: [805d849d7c3cc1f38efefd48b2480d62b7b5dcb7] Merge tag 'acpi-6.8-rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm > git bisect start '7f43e0f76e4710b2882c551519eff50e502115c5' '805d849d7c3cc1f38efefd48b2480d62b7b5dcb7' > # bad: [7e6ae2db7f319bf9613ec6db8fa3c9bc1de1b346] mm: add swappiness= arg to memory.reclaim > git bisect bad 7e6ae2db7f319bf9613ec6db8fa3c9bc1de1b346 > # good: [c6ec76a2ebc5829e5826b218d2e1475ec11b333e] mm: add pte_batch_hint() to reduce scanning in folio_pte_batch() > git bisect good c6ec76a2ebc5829e5826b218d2e1475ec11b333e > # good: [a02829f011b64e6c102929ed55da52e38391e970] writeback: fix done_index when hitting the wbc->nr_to_write > git bisect good a02829f011b64e6c102929ed55da52e38391e970 > # good: [de435b3b914686116f86494b8cb53224d7e24cc5] arm64/mm: improve comment in contpte_ptep_get_lockless() > git bisect good de435b3b914686116f86494b8cb53224d7e24cc5 > # good: [c143365caad5c3ad45662c393b9114c7cc694473] mm: handle large folios in free_unref_folios() > git bisect good c143365caad5c3ad45662c393b9114c7cc694473 > # skip: [ab6445067cfbaf4ac94e969f7e8e785049314099] mm: add alloc_contig_migrate_range allocation statistics > git bisect skip ab6445067cfbaf4ac94e969f7e8e785049314099 > # good: [447bf726277614396adcd4beedaf77ef74a748fa] modules: wait do_free_init correctly > git bisect good 447bf726277614396adcd4beedaf77ef74a748fa > # good: [cf2ac0c3998ffcbea680aeea2dee04d450654534] mm: remove PageWaiters, PageSetWaiters and PageClearWaiters > git bisect good cf2ac0c3998ffcbea680aeea2dee04d450654534 > # bad: [c48de1718df9dcafb08aefbc6a0edf46e2f94e66] mm: constify more page/folio tests > git bisect bad c48de1718df9dcafb08aefbc6a0edf46e2f94e66 > # bad: [48e4e7b8eea5fc80faad81515d429bce041f352d] mm: make dump_page() take a const argument > git bisect bad 48e4e7b8eea5fc80faad81515d429bce041f352d > # bad: [d67cd9f23139ddfd7e0ef1e18474c16445188433] mm: add __dump_folio() > git bisect bad d67cd9f23139ddfd7e0ef1e18474c16445188433 > # good: [e9844b2b6cf103f4f3a42119d62758eb26c5c233] mm: remove PageYoung and PageIdle definitions > git bisect good e9844b2b6cf103f4f3a42119d62758eb26c5c233 > # first bad commit: [d67cd9f23139ddfd7e0ef1e18474c16445188433] mm: add __dump_folio() > > Cheers, > Nathan _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel