x86/mm: restore early initialization of high_memory for 32-bits

Kernel test robot reports the following crash on 32-bit system with
HIGHMEM and DEBUG_VIRTUAL:

[    0.056128][    T0] kernel BUG at arch/x86/mm/physaddr.c:77!
PANIC: early exception 0x06 IP 60:c116539d error 0 cr2 0x0
[    0.056916][    T0] CPU: 0 UID: 0 PID: 0 Comm: swapper Not tainted 6.14.0-rc4-00010-ga4dbe5c71817 #1
[    0.057570][    T0] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
[ 0.058299][ T0] EIP: __phys_addr (arch/x86/mm/physaddr.c:77)
[ 0.058633][ T0] Code: 00 74 33 89 f0 e8 d3 8b 2e 00 89 c3 0f b6 d0 b8 58 bb 4b c5 31 c9 6a 00 e8 70 f5 15 00 83 c4 04 84 db 74 25 ff 05 78 de 5d c5 <0f> 0b b8 c8 91 ea c4 e8 e7 6e ea ff b8 58 bb 4b c5 31 d2 31 c9 6a
All code
[    0.060017][    T0] EAX: 00000000 EBX: c61f7001 ECX: 00000000 EDX: 00000000
[    0.060519][    T0] ESI: c61f7000 EDI: 061f7000 EBP: c4e31f04 ESP: c61f7000
[    0.061016][    T0] DS: 007b ES: 007b FS: 0000 GS: 0000 SS: cff4 EFLAGS: 00210002
[    0.061560][    T0] CR0: 80050033 CR2: 00000000 CR3: 059fc000 CR4: 00000090
[    0.062060][    T0] Call Trace:
[ 0.062288][ T0] ? show_regs (arch/x86/kernel/dumpstack.c:478)
[ 0.062588][ T0] ? early_fixup_exception (arch/x86/include/asm/nospec-branch.h:595)
[ 0.062968][ T0] ? early_idt_handler_common (arch/x86/kernel/head_32.S:352)
[ 0.063360][ T0] ? __phys_addr (arch/x86/mm/physaddr.c:77)
[ 0.063677][ T0] ? one_page_table_init (arch/x86/mm/init_32.c:100)
[ 0.064037][ T0] ? page_table_range_init (arch/x86/mm/init_32.c:227)
[ 0.064411][ T0] ? permanent_kmaps_init (include/linux/pgtable.h:191 include/linux/pgtable.h:196 arch/x86/mm/init_32.c:395)
[ 0.064814][ T0] ? paging_init (arch/x86/mm/init_32.c:677)
[ 0.065118][ T0] ? native_pagetable_init (arch/x86/mm/init_32.c:481)
[ 0.065503][ T0] ? setup_arch (arch/x86/kernel/setup.c:1131)
[ 0.065819][ T0] ? start_kernel (include/linux/jump_label.h:267 init/main.c:920)
[ 0.066143][ T0] ? i386_start_kernel (arch/x86/kernel/head32.c:79)
[ 0.066501][ T0] ? startup_32_smp (arch/x86/kernel/head_32.S:292)

The crash happens because commit e120d1b ("arch, mm: set high_memory
in free_area_init()") moved initialization of high_memory after
__vmalloc_start_set and with high_memory still set to 0 any address passes
is_vmalloc_addr() check.

Restore early initialization of high_memory on 32-bit systems in
initmem_init().

Link: https://lkml.kernel.org/r/20250319122337.1538924-1-rppt@kernel.org
Fixes: e120d1b ("arch, mm: set high_memory in free_area_init()")
Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
Reported-by: kernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202503191442.112e954f-lkp@intel.com
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Borislav Betkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleinxer <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

Author: rppt

arch/x86/mm/init_32.c

@@ -626,6 +626,9 @@ void __init initmem_init(void)
 		highstart_pfn = max_low_pfn;
 	printk(KERN_NOTICE "%ldMB HIGHMEM available.\n",
 		pages_to_mb(highend_pfn - highstart_pfn));
+	high_memory = (void *) __va(highstart_pfn * PAGE_SIZE - 1) + 1;
+#else
+	high_memory = (void *) __va(max_low_pfn * PAGE_SIZE - 1) + 1;
 #endif
 
 	memblock_set_node(0, PHYS_ADDR_MAX, &memblock.memory, 0);

arch/x86/mm/numa_32.c

@@ -41,6 +41,9 @@ void __init initmem_init(void)
 		highstart_pfn = max_low_pfn;
 	printk(KERN_NOTICE "%ldMB HIGHMEM available.\n",
 	       pages_to_mb(highend_pfn - highstart_pfn));
+	high_memory = (void *) __va(highstart_pfn * PAGE_SIZE - 1) + 1;
+#else
+	high_memory = (void *) __va(max_low_pfn * PAGE_SIZE - 1) + 1;
 #endif
 	printk(KERN_NOTICE "%ldMB LOWMEM available.\n",
 			pages_to_mb(max_low_pfn));