From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 696B320316 for ; Mon, 6 Nov 2023 13:14:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="cGdXny7D" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 95D39C433C9; Mon, 6 Nov 2023 13:14:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1699276444; bh=Ld2JKp9QAMLVBWhIdKoXU9wXdi5SnoO3eRVrWt8jWgs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=cGdXny7DbTHA96R33htY00nrEwhnCT23PYiiOSsaGj4G5p/5jYOTpb6voXVUfD8xd KpSN0xnqpC1dZm8qq6EpJMCyl5cZcB8D4DUPel0Dyultx9rvkHD4OgmT5fnmRbX/w2 j6LWvMiSxp9+pzjhhcBOcMFeGg6zEzUHmc8MwbQc= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Erhard Furtner , Michael Ellerman , Sasha Levin Subject: [PATCH 6.1 37/62] powerpc/mm: Fix boot crash with FLATMEM Date: Mon, 6 Nov 2023 14:03:43 +0100 Message-ID: <20231106130303.168836140@linuxfoundation.org> X-Mailer: git-send-email 2.42.0 In-Reply-To: <20231106130301.807965064@linuxfoundation.org> References: <20231106130301.807965064@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.1-stable review patch. If anyone has any objections, please let me know. ------------------ From: Michael Ellerman [ Upstream commit daa9ada2093ed23d52b4c1fe6e13cf78f55cc85f ] Erhard reported that his G5 was crashing with v6.6-rc kernels: mpic: Setting up HT PICs workarounds for U3/U4 BUG: Unable to handle kernel data access at 0xfeffbb62ffec65fe Faulting instruction address: 0xc00000000005dc40 Oops: Kernel access of bad area, sig: 11 [#1] BE PAGE_SIZE=4K MMU=Hash SMP NR_CPUS=2 PowerMac Modules linked in: CPU: 0 PID: 0 Comm: swapper/0 Tainted: G T 6.6.0-rc3-PMacGS #1 Hardware name: PowerMac11,2 PPC970MP 0x440101 PowerMac NIP: c00000000005dc40 LR: c000000000066660 CTR: c000000000007730 REGS: c0000000022bf510 TRAP: 0380 Tainted: G T (6.6.0-rc3-PMacGS) MSR: 9000000000001032 CR: 44004242 XER: 00000000 IRQMASK: 3 GPR00: 0000000000000000 c0000000022bf7b0 c0000000010c0b00 00000000000001ac GPR04: 0000000003c80000 0000000000000300 c0000000f20001ae 0000000000000300 GPR08: 0000000000000006 feffbb62ffec65ff 0000000000000001 0000000000000000 GPR12: 9000000000001032 c000000002362000 c000000000f76b80 000000000349ecd8 GPR16: 0000000002367ba8 0000000002367f08 0000000000000006 0000000000000000 GPR20: 00000000000001ac c000000000f6f920 c0000000022cd985 000000000000000c GPR24: 0000000000000300 00000003b0a3691d c0003e008030000e 0000000000000000 GPR28: c00000000000000c c0000000f20001ee feffbb62ffec65fe 00000000000001ac NIP hash_page_do_lazy_icache+0x50/0x100 LR __hash_page_4K+0x420/0x590 Call Trace: hash_page_mm+0x364/0x6f0 do_hash_fault+0x114/0x2b0 data_access_common_virt+0x198/0x1f0 --- interrupt: 300 at mpic_init+0x4bc/0x10c4 NIP: c000000002020a5c LR: c000000002020a04 CTR: 0000000000000000 REGS: c0000000022bf9f0 TRAP: 0300 Tainted: G T (6.6.0-rc3-PMacGS) MSR: 9000000000001032 CR: 24004248 XER: 00000000 DAR: c0003e008030000e DSISR: 40000000 IRQMASK: 1 ... NIP mpic_init+0x4bc/0x10c4 LR mpic_init+0x464/0x10c4 --- interrupt: 300 pmac_setup_one_mpic+0x258/0x2dc pmac_pic_init+0x28c/0x3d8 init_IRQ+0x90/0x140 start_kernel+0x57c/0x78c start_here_common+0x1c/0x20 A bisect pointed to the breakage beginning with commit 9fee28baa601 ("powerpc: implement the new page table range API"). Analysis of the oops pointed to a struct page with a corrupted compound_head being loaded via page_folio() -> _compound_head() in hash_page_do_lazy_icache(). The access by the mpic code is to an MMIO address, so the expectation is that the struct page for that address would be initialised by init_unavailable_range(), as pointed out by Aneesh. Instrumentation showed that was not the case, which eventually lead to the realisation that pfn_valid() was returning false for that address, causing the struct page to not be initialised. Because the system is using FLATMEM, the version of pfn_valid() in memory_model.h is used: static inline int pfn_valid(unsigned long pfn) { ... return pfn >= pfn_offset && (pfn - pfn_offset) < max_mapnr; } Which relies on max_mapnr being initialised. Early in boot max_mapnr is zero meaning no PFNs are valid. max_mapnr is initialised in mem_init() called via: start_kernel() mm_core_init() # init/main.c:928 mem_init() But that is too late for the usage in init_unavailable_range() called via: start_kernel() setup_arch() # init/main.c:893 paging_init() free_area_init() init_unavailable_range() Although max_mapnr is currently set in mem_init(), the value is actually already available much earlier, as soon as mem_topology_setup() has completed, which is also before paging_init() is called. So move the initialisation there, which causes paging_init() to correctly initialise the struct page and fixes the bug. This bug seems to have been lurking for years, but went unnoticed because the pre-folio code was inspecting the uninitialised page->flags but not dereferencing it. Thanks to Erhard and Aneesh for help debugging. Reported-by: Erhard Furtner Closes: https://lore.kernel.org/all/20230929132750.3cd98452@yea/ Signed-off-by: Michael Ellerman Link: https://msgid.link/20231023112500.1550208-1-mpe@ellerman.id.au Signed-off-by: Sasha Levin --- arch/powerpc/kernel/setup-common.c | 2 ++ arch/powerpc/mm/mem.c | 1 - 2 files changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/powerpc/kernel/setup-common.c b/arch/powerpc/kernel/setup-common.c index efb301a4987ca..59b4ac57bfaf7 100644 --- a/arch/powerpc/kernel/setup-common.c +++ b/arch/powerpc/kernel/setup-common.c @@ -946,6 +946,8 @@ void __init setup_arch(char **cmdline_p) /* Parse memory topology */ mem_topology_setup(); + /* Set max_mapnr before paging_init() */ + set_max_mapnr(max_pfn); /* * Release secondary cpus out of their spinloops at 0x60 now that diff --git a/arch/powerpc/mm/mem.c b/arch/powerpc/mm/mem.c index 84d171953ba44..c7599b1737099 100644 --- a/arch/powerpc/mm/mem.c +++ b/arch/powerpc/mm/mem.c @@ -288,7 +288,6 @@ void __init mem_init(void) #endif high_memory = (void *) __va(max_low_pfn * PAGE_SIZE); - set_max_mapnr(max_pfn); kasan_late_init(); -- 2.42.0