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 03B0BC5475B for ; Fri, 1 Mar 2024 09:47:56 +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=rHhUp1nfgh0n+r+hSE86gFfiGNggrJJCdwMl58YzsCk=; b=oug866MMIG0Rd2 WqjxKzZsAtEUt9bL/vJJH+PK3nvg95iZiGvhewWlKfiw6dYAAb2volTJBN2qT50T4cmNeZ2hd9raq IxwdVTitLaKGIA5yEyFyfb4WzxvKEA6qRkJqCD1fAJAIGYi9vXW/VgsYeSe+WvOqyu8zNRxP8clqF sDibqFbZ62hAqkN16Zy6GryscMA7QIylsPL51BqWD2U3JrEmtQws+UcDV3qI1trmbprtWjt0kft+v OZRxqkam+2KZk186EKjq+LMmzE4rkNCrCoDX6mloKUcedJoX5YqwcIi17zSE2+mBAspKJXUX6ThuW NHEzoOkieoIieu1JAy8A==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rfzUV-0000000HEJb-2y9e; Fri, 01 Mar 2024 09:47:43 +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 1rfzUS-0000000HEIN-2hdu for linux-arm-kernel@lists.infradead.org; Fri, 01 Mar 2024 09:47:42 +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 AA1761FB; Fri, 1 Mar 2024 01:48:16 -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 54A9B3F762; Fri, 1 Mar 2024 01:47:35 -0800 (PST) Message-ID: Date: Fri, 1 Mar 2024 09:47:33 +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: Ard Biesheuvel Cc: Nathan Chancellor , Matthew Wilcox , Ard Biesheuvel , linux-arm-kernel@lists.infradead.org, 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> <133a91b8-bc8b-42b3-afcd-595d7f45db84@arm.com> From: Ryan Roberts In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240301_014740_828738_E0301E20 X-CRM114-Status: GOOD ( 33.19 ) 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 On 01/03/2024 09:37, Ard Biesheuvel wrote: > On Fri, 1 Mar 2024 at 10:10, Ard Biesheuvel wrote: >> >> On Fri, 1 Mar 2024 at 09:54, Ryan Roberts wrote: >>> >>> + 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(). >>> >> >> Yes, there are clearly two different issues at play here. The NULL >> dereference might be an issue in the __dump_page() patch, but going >> down that code path in the first place seems like it might be a >> problem with mine. >> >> The mapcount of -512 looks interesting as well. >> >>> 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. >>> >> > > The crash does not reproduce for me, but the warning can be fixed by > > diff --git a/arch/arm64/include/asm/pgalloc.h b/arch/arm64/include/asm/pgalloc.h > index aeba2cf15a25..78f30b782889 100644 > --- a/arch/arm64/include/asm/pgalloc.h > +++ b/arch/arm64/include/asm/pgalloc.h > @@ -61,7 +61,7 @@ static inline void pud_free(struct mm_struct *mm, pud_t *pud) > if (!pgtable_l4_enabled()) > return; > BUG_ON((unsigned long)pud & (PAGE_SIZE-1)); > - free_page((unsigned long)pud); > + __pud_free(mm, pud); > } > #else > static inline void __p4d_populate(p4d_t *p4dp, phys_addr_t pudp, p4dval_t prot) > > I'll send this out as a patch shortly. Great thanks! I'm pretty sure I've found the bug in Matthew's patch - it is copying the struct page to the stack to avoid a potential race, but later some macros are hiding a page_to_pfn(). Since the page's address is on the stack, I reckon that's giving a bogus pfn. Just confirming and writing it up and will send against the original patch shortly. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel