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 B3E8FC00528 for ; Mon, 24 Jul 2023 18:18:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229675AbjGXSS1 (ORCPT ); Mon, 24 Jul 2023 14:18:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38458 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229862AbjGXSS0 (ORCPT ); Mon, 24 Jul 2023 14:18:26 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:3::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id ABB0FE4E; Mon, 24 Jul 2023 11:18:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Sender:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=FftEnjrfbBAd3Ww9EqN8sppXbEA0boEKYQQaC3XYChY=; b=ALkl62CiRE28E2LSizMN3y7fEY kJycbVRJZEvZWmguJTa9cV8saw4voW845Dk7ZUIQ/EpBqHehcYEObAuEhAbV5cICUXMxpEHgWD1xY 0G6eQD7tzvNPI+5LLNz+rczyJT/b6KyVcZ+bYO3jrw6raTDm6jxMaJpIvIG1XxtiGTStkaoeXQ5ux i2K6PllfRHRUSgqlIGCCkFHMYoEy4mFvIGC8wSVGTqOtUaudgrq/YQeHfsLxDw4QBvQ2/XP3rLron /nYKqQX7yUCVJiO+cQev86wNP91/7Iz+oGCh9AS1aLKpPK5iq4sDhzycio7fP17V8xO0Lv6e1RKak XdsSA3Lg==; Received: from mcgrof by bombadil.infradead.org with local (Exim 4.96 #2 (Red Hat Linux)) id 1qO08S-005BNK-31; Mon, 24 Jul 2023 18:18:20 +0000 Date: Mon, 24 Jul 2023 11:18:20 -0700 From: Luis Chamberlain To: Alistair Popple , linux-fsdevel@vger.kernel.org, linux-xfs@vger.kernel.org, Pankaj Raghav Cc: SeongJae Park , kevin.tian@intel.com, x86@kernel.org, ajd@linux.ibm.com, kvm@vger.kernel.org, linux-mm@kvack.org, catalin.marinas@arm.com, seanjc@google.com, will@kernel.org, linux-kernel@vger.kernel.org, npiggin@gmail.com, zhi.wang.linux@gmail.com, jgg@ziepe.ca, iommu@lists.linux.dev, nicolinc@nvidia.com, jhubbard@nvidia.com, fbarrat@linux.ibm.com, akpm@linux-foundation.org, linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, robin.murphy@arm.com, mcgrof@kernel.org Subject: Re: [PATCH v2 3/5] mmu_notifiers: Call invalidate_range() when invalidating TLBs Message-ID: References: <8f293bb51a423afa71ddc3ba46e9f323ee9ffbc7.1689768831.git-series.apopple@nvidia.com> <20230719225105.1934-1-sj@kernel.org> <877cqvl7vr.fsf@nvdebian.thelocal> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <877cqvl7vr.fsf@nvdebian.thelocal> Sender: Luis Chamberlain Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Cc'ing fsdevel + xfs folks as this fixes a regression tests with XFS with generic/176. On Thu, Jul 20, 2023 at 10:52:59AM +1000, Alistair Popple wrote: > > SeongJae Park writes: > > > Hi Alistair, > > > > On Wed, 19 Jul 2023 22:18:44 +1000 Alistair Popple wrote: > > > >> The invalidate_range() is going to become an architecture specific mmu > >> notifier used to keep the TLB of secondary MMUs such as an IOMMU in > >> sync with the CPU page tables. Currently it is called from separate > >> code paths to the main CPU TLB invalidations. This can lead to a > >> secondary TLB not getting invalidated when required and makes it hard > >> to reason about when exactly the secondary TLB is invalidated. > >> > >> To fix this move the notifier call to the architecture specific TLB > >> maintenance functions for architectures that have secondary MMUs > >> requiring explicit software invalidations. > >> > >> This fixes a SMMU bug on ARM64. On ARM64 PTE permission upgrades > >> require a TLB invalidation. This invalidation is done by the > >> architecutre specific ptep_set_access_flags() which calls > >> flush_tlb_page() if required. However this doesn't call the notifier > >> resulting in infinite faults being generated by devices using the SMMU > >> if it has previously cached a read-only PTE in it's TLB. > >> > >> Moving the invalidations into the TLB invalidation functions ensures > >> all invalidations happen at the same time as the CPU invalidation. The > >> architecture specific flush_tlb_all() routines do not call the > >> notifier as none of the IOMMUs require this. > >> > >> Signed-off-by: Alistair Popple > >> Suggested-by: Jason Gunthorpe > > > > I found below kernel NULL-dereference issue on latest mm-unstable tree, and > > bisect points me to the commit of this patch, namely > > 75c400f82d347af1307010a3e06f3aa5d831d995. > > > > To reproduce, I use 'stress-ng --bigheap $(nproc)'. The issue happens as soon > > as it starts reclaiming memory. I didn't dive deep into this yet, but > > reporting this issue first, since you might have an idea already. > > Thanks for the report SJ! > > I see the problem - current->mm can (obviously!) be NULL which is what's > leading to the NULL dereference. Instead I think on x86 I need to call > the notifier when adding the invalidate to the tlbbatch in > arch_tlbbatch_add_pending() which is equivalent to what ARM64 does. > > The below should fix it. Will do a respin with this. > > --- > > diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h > index 837e4a50281a..79c46da919b9 100644 > --- a/arch/x86/include/asm/tlbflush.h > +++ b/arch/x86/include/asm/tlbflush.h > @@ -4,6 +4,7 @@ > > #include > #include > +#include > > #include > #include > @@ -282,6 +283,7 @@ static inline void arch_tlbbatch_add_pending(struct arch_tlbflush_unmap_batch *b > { > inc_mm_tlb_gen(mm); > cpumask_or(&batch->cpumask, &batch->cpumask, mm_cpumask(mm)); > + mmu_notifier_arch_invalidate_secondary_tlbs(mm, 0, -1UL); > } > > static inline void arch_flush_tlb_batched_pending(struct mm_struct *mm) > diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c > index 0b990fb56b66..2d253919b3e8 100644 > --- a/arch/x86/mm/tlb.c > +++ b/arch/x86/mm/tlb.c > @@ -1265,7 +1265,6 @@ void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch) > > put_flush_tlb_info(); > put_cpu(); > - mmu_notifier_arch_invalidate_secondary_tlbs(current->mm, 0, -1UL); > } > > /* This patch also fixes a regression introduced on linux-next, the same crash on arch_tlbbatch_flush() is reproducible with fstests generic/176 on XFS. This patch fixes that regression [0]. This should also close out the syzbot crash too [1] [0] https://gist.github.com/mcgrof/b37fc8cf7e6e1b3935242681de1a83e2 [1] https://lore.kernel.org/all/0000000000003afcb4060135a664@google.com/ Tested-by: Luis Chamberlain Luis