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Peter Anvin" , Paolo Bonzini , Sean Christopherson , Thomas Gleixner , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org Subject: Re: [PATCH] x86/e820: discard high memory that can't be addressed by 32-bit systems Message-ID: References: <20250413080858.743221-1-rppt@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250413080858.743221-1-rppt@kernel.org> Hi, On Sun, Apr 13, 2025 at 11:08:58AM +0300, Mike Rapoport wrote: > From: "Mike Rapoport (Microsoft)" > > Dave Hansen reports the following crash on a 32-bit system with > CONFIG_HIGHMEM=y and CONFIG_X86_PAE=y: > > > 0xf75fe000 is the mem_map[] entry for the first page >4GB. It > > obviously wasn't allocated, thus the oops. > > BUG: unable to handle page fault for address: f75fe000 > #PF: supervisor write access in kernel mode > #PF: error_code(0x0002) - not-present page > *pdpt = 0000000002da2001 *pde = 000000000300c067 *pte = 0000000000000000 > Oops: Oops: 0002 [#1] SMP NOPTI > CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 6.15.0-rc1-00288-ge618ee89561b-dirty #311 PREEMPT(undef) > Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014 > EIP: __free_pages_core+0x3c/0x74 > Code: c3 d3 e6 83 ec 10 89 44 24 08 89 74 24 04 c7 04 24 c6 32 3a c2 89 55 f4 e8 a9 11 45 fe 85 f6 8b 55 f4 74 19 89 d8 31 c9 66 90 <0f> ba 30 0d c7 40 1c 00 00 00 00 41 83 c0 28 39 ce 75 ed 8b > > EAX: f75fe000 EBX: f75fe000 ECX: 00000000 EDX: 0000000a > ESI: 00000400 EDI: 00500000 EBP: c247becc ESP: c247beb4 > DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 EFLAGS: 00210046 > CR0: 80050033 CR2: f75fe000 CR3: 02da6000 CR4: 000000b0 > Call Trace: > memblock_free_pages+0x11/0x2c > memblock_free_all+0x2ce/0x3a0 > mm_core_init+0xf5/0x320 > start_kernel+0x296/0x79c > ? set_init_arg+0x70/0x70 > ? load_ucode_bsp+0x13c/0x1a8 > i386_start_kernel+0xad/0xb0 > startup_32_smp+0x151/0x154 > Modules linked in: > CR2: 00000000f75fe000 > > The mem_map[] is allocated up to the end of ZONE_HIGHMEM which is defined > by max_pfn. > > Before 6faea3422e3b ("arch, mm: streamline HIGHMEM freeing") freeing of > high memory was also clamped to the end of ZONE_HIGHMEM but after > 6faea3422e3b memblock_free_all() tries to free memory above the of > ZONE_HIGHMEM as well and that causes access to mem_map[] entries beyond > the end of the memory map. > > Discard the memory after max_pfn from memblock on 32-bit systems so that > core MM would be aware only of actually usable memory. > > Reported-by: Dave Hansen > Tested-by: Arnd Bergmann > Signed-off-by: Mike Rapoport (Microsoft) With this patch in pending-fixes ( v6.15-rc2-434-g93ced5296772), all my i386 test runs crash. [ 0.020893] Kernel panic - not syncing: ioapic_setup_resources: Failed to allocate 0x0000002b bytes [ 0.021248] CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 6.15.0-rc2-00434-g93ced5296772 #1 PREEMPT(undef) [ 0.021373] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 [ 0.021549] Call Trace: [ 0.021711] dump_stack_lvl+0x20/0x104 [ 0.022023] dump_stack+0x12/0x18 [ 0.022064] panic+0x2c1/0x2d8 [ 0.022116] ? vprintk_default+0x29/0x30 [ 0.022163] __memblock_alloc_or_panic+0x57/0x58 [ 0.022221] io_apic_init_mappings+0x2e/0x1a8 [ 0.022284] setup_arch+0x909/0xdac [ 0.022338] ? vprintk_default+0x29/0x30 [ 0.022410] start_kernel+0x63/0x760 [ 0.022457] ? load_ucode_bsp+0x12c/0x198 [ 0.022507] i386_start_kernel+0x74/0x74 [ 0.022548] startup_32_smp+0x151/0x154 [ 0.023089] ---[ end Kernel panic - not syncing: ioapic_setup_resources: Failed to allocate 0x0000002b bytes ]--- Reverting this patch fixes the problem. Bisect log is attached for reference. Guenter --- # bad: [93ced5296772b7b704f48e4bad9fcfdf0633c780] Merge branch 'for-linux-next-fixes' of https://gitlab.freedesktop.org/drm/misc/kernel.git # good: [8ffd015db85fea3e15a77027fda6c02ced4d2444] Linux 6.15-rc2 git bisect start 'HEAD' 'v6.15-rc2' # good: [5d6f363fc974e32dd9930fecaae63958b68a1df4] Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regmap.git git bisect good 5d6f363fc974e32dd9930fecaae63958b68a1df4 # good: [1790b4a242fe119fead08fccc5bf923423c7449a] Merge branch 'dma-mapping-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/mszyprowski/linux.git git bisect good 1790b4a242fe119fead08fccc5bf923423c7449a # good: [5d37ee8a1d6455968ea3134d78223090d487c7f4] Merge branch 'fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux.git git bisect good 5d37ee8a1d6455968ea3134d78223090d487c7f4 # good: [9d4de5ae5208548eb9c6a490ac454601f4fbf00b] Merge branch 'i2c/i2c-host-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/andi.shyti/linux.git git bisect good 9d4de5ae5208548eb9c6a490ac454601f4fbf00b # bad: [f737ab93945fb8f0213e1cccc39d028eb5d880e0] Merge branch into tip/master: 'x86/urgent' git bisect bad f737ab93945fb8f0213e1cccc39d028eb5d880e0 # good: [2e7a2843d0de7677b7bb908ca006dc435e52c416] Merge branch into tip/master: 'irq/urgent' git bisect good 2e7a2843d0de7677b7bb908ca006dc435e52c416 # good: [d466304c4322ad391797437cd84cca7ce1660de0] x86/cpu: Add CPU model number for Bartlett Lake CPUs with Raptor Cove cores git bisect good d466304c4322ad391797437cd84cca7ce1660de0 # good: [39893b1e4ad7c4380abe4cfddaa58b34c4363bf4] Merge branch into tip/master: 'timers/urgent' git bisect good 39893b1e4ad7c4380abe4cfddaa58b34c4363bf4 # bad: [1e07b9fad022e0e02215150ca1e20912e78e8ec1] x86/e820: Discard high memory that can't be addressed by 32-bit systems git bisect bad 1e07b9fad022e0e02215150ca1e20912e78e8ec1 # first bad commit: [1e07b9fad022e0e02215150ca1e20912e78e8ec1] x86/e820: Discard high memory that can't be addressed by 32-bit systems