linux-kernel - Re: [PATCH 05/11] x86: remove HIGHMEM64G support

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Message-ID: <08b63835-121d-4adc-8f03-e68f0b0cabdf@intel.com>
Date: Fri, 11 Apr 2025 16:44:13 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Arnd Bergmann <arnd@...nel.org>, linux-kernel@...r.kernel.org,
 x86@...nel.org
Cc: Arnd Bergmann <arnd@...db.de>, Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
 Dave Hansen <dave.hansen@...ux.intel.com>, "H. Peter Anvin" <hpa@...or.com>,
 Linus Torvalds <torvalds@...ux-foundation.org>,
 Andy Shevchenko <andy@...nel.org>, Matthew Wilcox <willy@...radead.org>,
 Sean Christopherson <seanjc@...gle.com>,
 Davide Ciminaghi <ciminaghi@...dd.com>, Paolo Bonzini <pbonzini@...hat.com>,
 kvm@...r.kernel.org, Mike Rapoport <rppt@...nel.org>
Subject: Re: [PATCH 05/11] x86: remove HIGHMEM64G support

Has anyone run into any problems on 6.15-rc1 with this stuff?

0xf75fe000 is the mem_map[] entry for the first page >4GB. It obviously
wasn't allocated, thus the oops. Looks like the memblock for the >4GB
memory didn't get removed although the pgdats seem correct.

I'll dig into it some more. Just wanted to make sure there wasn't a fix
out there already.

The way I'm triggering this is booting qemu with a 32-bit PAE kernel,
and "-m 4096" (or more).

> [    0.003806] Warning: only 4GB will be used. Support for for CONFIG_HIGHMEM64G was removed!
...
> [    0.561310] BUG: unable to handle page fault for address: f75fe000
> [    0.562226] #PF: supervisor write access in kernel mode
> [    0.562947] #PF: error_code(0x0002) - not-present page
> [    0.563653] *pdpt = 0000000002da2001 *pde = 000000000300c067 *pte = 0000000000000000 
> [    0.564728] Oops: Oops: 0002 [#1] SMP NOPTI
> [    0.565315] CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 6.15.0-rc1-00288-ge618ee89561b-dirty #311 PREEMPT(undef) 
> [    0.567428] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
> [    0.568777] EIP: __free_pages_core+0x3c/0x74
> [    0.569378] 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 03 c1
> [    0.571943] EAX: f75fe000 EBX: f75fe000 ECX: 00000000 EDX: 0000000a
> [    0.572806] ESI: 00000400 EDI: 00500000 EBP: c247becc ESP: c247beb4
> [    0.573776] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 EFLAGS: 00210046
> [    0.574606] CR0: 80050033 CR2: f75fe000 CR3: 02da6000 CR4: 000000b0
> [    0.575464] Call Trace:
> [    0.575816]  memblock_free_pages+0x11/0x2c
> [    0.576392]  memblock_free_all+0x2ce/0x3a0
> [    0.576955]  mm_core_init+0xf5/0x320
> [    0.577423]  start_kernel+0x296/0x79c
> [    0.577950]  ? set_init_arg+0x70/0x70
> [    0.578478]  ? load_ucode_bsp+0x13c/0x1a8
> [    0.579059]  i386_start_kernel+0xad/0xb0
> [    0.579614]  startup_32_smp+0x151/0x154
> [    0.580100] Modules linked in:
> [    0.580358] CR2: 00000000f75fe000
> [    0.580630] ---[ end trace 0000000000000000 ]---
> [    0.581111] EIP: __free_pages_core+0x3c/0x74
> [    0.581455] 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 03 c1
> [    0.584767] EAX: f75fe000 EBX: f75fe000 ECX: 00000000 EDX: 0000000a
> [    0.585651] ESI: 00000400 EDI: 00500000 EBP: c247becc ESP: c247beb4
> [    0.586530] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 EFLAGS: 00210046
> [    0.587480] CR0: 80050033 CR2: f75fe000 CR3: 02da6000 CR4: 000000b0
> [    0.588344] Kernel panic - not syncing: Attempted to kill the idle task!
> [    0.589435] ---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]---

> [    0.561310] BUG: unable to handle page fault for address: f75fe000
> [    0.562226] #PF: supervisor write access in kernel mode
> [    0.562947] #PF: error_code(0x0002) - not-present page
> [    0.563653] *pdpt = 0000000002da2001 *pde = 000000000300c067 *pte = 0000000000000000 
> [    0.564728] Oops: Oops: 0002 [#1] SMP NOPTI
> [    0.565315] CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 6.15.0-rc1-00288-ge618ee89561b-dirty #311 PREEMPT(undef) 
> [    0.567428] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
> [    0.568777] EIP: __free_pages_core+0x3c/0x74
> [    0.569378] 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 03 c1
> [    0.571943] EAX: f75fe000 EBX: f75fe000 ECX: 00000000 EDX: 0000000a
> [    0.572806] ESI: 00000400 EDI: 00500000 EBP: c247becc ESP: c247beb4
> [    0.573776] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 EFLAGS: 00210046
> [    0.574606] CR0: 80050033 CR2: f75fe000 CR3: 02da6000 CR4: 000000b0
> [    0.575464] Call Trace:
> [    0.575816]  memblock_free_pages+0x11/0x2c
> [    0.576392]  memblock_free_all+0x2ce/0x3a0
> [    0.576955]  mm_core_init+0xf5/0x320
> [    0.577423]  start_kernel+0x296/0x79c
> [    0.577950]  ? set_init_arg+0x70/0x70
> [    0.578478]  ? load_ucode_bsp+0x13c/0x1a8
> [    0.579059]  i386_start_kernel+0xad/0xb0
> [    0.579614]  startup_32_smp+0x151/0x154
> [    0.580100] Modules linked in:
> [    0.580358] CR2: 00000000f75fe000
> [    0.580630] ---[ end trace 0000000000000000 ]---
> [    0.581111] EIP: __free_pages_core+0x3c/0x74
> [    0.581455] 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 03 c1
> [    0.584767] EAX: f75fe000 EBX: f75fe000 ECX: 00000000 EDX: 0000000a
> [    0.585651] ESI: 00000400 EDI: 00500000 EBP: c247becc ESP: c247beb4
> [    0.586530] DS: 007b ES: 007b FS: 00d8 GS: 0000 SS: 0068 EFLAGS: 00210046
> [    0.587480] CR0: 80050033 CR2: f75fe000 CR3: 02da6000 CR4: 000000b0
> [    0.588344] Kernel panic - not syncing: Attempted to kill the idle task!
> [    0.589435] ---[ end Kernel panic - not syncing: Attempted to kill the idle task! ]---