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Peter Anvin" , Ingo Molnar , Michal Hocko , Peter Zijlstra , Qi Zheng , Thomas Gleixner , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] x86/mm: drop 4MB restriction on minimal NUMA node size Message-ID: <20231017075246.GA2824@kernel.org> References: <20231017062215.171670-1-rppt@kernel.org> <4207feb8-be8c-4d49-b880-31366c0414cb@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4207feb8-be8c-4d49-b880-31366c0414cb@redhat.com> X-Rspamd-Queue-Id: 2912240017 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: xqjrf5rg7cc7x4by8zd34pd1n8tqykt5 X-HE-Tag: 1697529181-378540 X-HE-Meta: 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 nz/8BYyC Sae/LdFFVXDajIffL18e5iNhlaZ12KQ2h5GieB2d7es5PwXfYxbq4+1oLTlt3gxs5krleM/M35kcbDs/Z8TmxBIxvGSqbFNE7kymnH03cprKmsU86mQzUhRX6W6cLDwaBkouhSRmjyvWXb0pKdznYb0WvD2aFAp2DzhSIOAppI8uoDa+Bh+t3gb0rXdyNL5hASizJsRh2adkEHYiRCMLnZLZvqIzub7BWBY9WNjCEdSCidj7rchVVtCe397V2MX9+TjhlWBnmb06Fzyw34Cg9znTak/ivY7BEqysqKIVv3LrK9hqsxKg0pO/D7RLSz4Jk97uOl/EJw75BsSE/E815+7nTVHfxVsThtuG+DLyU0EZXpvyyyRRqy7heZ/gnlWj6uwhnfcEiPf09Zxo= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Oct 17, 2023 at 09:28:14AM +0200, David Hildenbrand wrote: > On 17.10.23 08:22, Mike Rapoport wrote: > > From: "Mike Rapoport (IBM)" > > > > Qi Zheng reports crashes in a production environment and provides a > > simplified example as a reproducer: > > > > For example, if we use qemu to start a two NUMA node kernel, > > one of the nodes has 2M memory (less than NODE_MIN_SIZE), > > and the other node has 2G, then we will encounter the > > following panic: > > > > [ 0.149844] BUG: kernel NULL pointer dereference, address: 0000000000000000 > > [ 0.150783] #PF: supervisor write access in kernel mode > > [ 0.151488] #PF: error_code(0x0002) - not-present page > > <...> > > [ 0.156056] RIP: 0010:_raw_spin_lock_irqsave+0x22/0x40 > > <...> > > [ 0.169781] Call Trace: > > [ 0.170159] > > [ 0.170448] deactivate_slab+0x187/0x3c0 > > [ 0.171031] ? bootstrap+0x1b/0x10e > > [ 0.171559] ? preempt_count_sub+0x9/0xa0 > > [ 0.172145] ? kmem_cache_alloc+0x12c/0x440 > > [ 0.172735] ? bootstrap+0x1b/0x10e > > [ 0.173236] bootstrap+0x6b/0x10e > > [ 0.173720] kmem_cache_init+0x10a/0x188 > > [ 0.174240] start_kernel+0x415/0x6ac > > [ 0.174738] secondary_startup_64_no_verify+0xe0/0xeb > > [ 0.175417] > > [ 0.175713] Modules linked in: > > [ 0.176117] CR2: 0000000000000000 > > > > The crashes happen because of inconsistency between nodemask that has > > nodes with less than 4MB as memoryless and the actual memory fed into > > core mm. > > > > The commit 9391a3f9c7f1 ("[PATCH] x86_64: Clear more state when ignoring > > empty node in SRAT parsing") that introduced minimal size of a NUMA node > > does not explain why a node size cannot be less than 4MB and what boot > > failures this restriction might fix. > > > > Since then a lot has changed and core mm won't confuse badly about small > > node sizes. > > > > Drop the limitation for the minimal node size. > > > > Reported-by: Qi Zheng > > Signed-off-by: Mike Rapoport (IBM) > > Acked-by: David Hildenbrand > > Acked-by: Michal Hocko > > Link: https://lore.kernel.org/all/20230212110305.93670-1-zhengqi.arch@bytedance.com/ > > That's just a resend I assume? Or has anything changed? Oh, I forgot RESEND prefix, sorry > -- > Cheers, > > David / dhildenb > -- Sincerely yours, Mike.