From 4d8e5a682be4136758a8beadd5aecc7f76276504 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Thu, 15 May 2025 14:05:21 +0200 Subject: [PATCH] x86/boot/e820: Print gaps in the E820 table Gaps in the E820 table are not obvious at a glance and can easily be overlooked. Print out gaps in the E820 table: Before: BIOS-provided physical RAM map: BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved BIOS-e820: [mem 0x0000000000100000-0x000000007ffdbfff] usable BIOS-e820: [mem 0x000000007ffdc000-0x000000007fffffff] reserved BIOS-e820: [mem 0x00000000b0000000-0x00000000bfffffff] reserved BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed1ffff] reserved BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff] reserved BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved BIOS-e820: [mem 0x000000fd00000000-0x000000ffffffffff] reserved After: BIOS-provided physical RAM map: BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved BIOS-e820: [gap 0x00000000000a0000-0x00000000000effff] BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved BIOS-e820: [mem 0x0000000000100000-0x000000007ffdbfff] usable BIOS-e820: [mem 0x000000007ffdc000-0x000000007fffffff] reserved BIOS-e820: [gap 0x0000000080000000-0x00000000afffffff] BIOS-e820: [mem 0x00000000b0000000-0x00000000bfffffff] reserved BIOS-e820: [gap 0x00000000c0000000-0x00000000fed1bfff] BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed1ffff] reserved BIOS-e820: [gap 0x00000000fed20000-0x00000000feffbfff] BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff] reserved BIOS-e820: [gap 0x00000000ff000000-0x00000000fffbffff] BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] reserved BIOS-e820: [gap 0x0000000100000000-0x000000fcffffffff] BIOS-e820: [mem 0x000000fd00000000-0x000000ffffffffff] reserved Also warn about badly ordered E820 table entries: BUG: out of order E820 entry! ( this is printed before the entry is printed, so there's no need to print any additional data with the warning. ) Signed-off-by: Ingo Molnar Cc: H . Peter Anvin Cc: Andy Shevchenko Cc: Arnd Bergmann Cc: David Woodhouse Cc: Juergen Gross Cc: Kees Cook Cc: Linus Torvalds Cc: Mike Rapoport Cc: Paul Menzel Cc: Peter Zijlstra Link: https://patch.msgid.link/20250515120549.2820541-6-mingo@kernel.org --- arch/x86/kernel/e820.c | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c index 09c712aec2d00..460645d09c6cf 100644 --- a/arch/x86/kernel/e820.c +++ b/arch/x86/kernel/e820.c @@ -202,18 +202,32 @@ static void __init e820_print_type(enum e820_type type) static void __init e820__print_table(const char *who) { + u64 range_end_prev = 0; int i; for (i = 0; i < e820_table->nr_entries; i++) { struct e820_entry *entry = e820_table->entries + i; + u64 range_start, range_end; - pr_info("%s: [mem %#018Lx-%#018Lx] ", - who, - entry->addr, - entry->addr + entry->size-1); + range_start = entry->addr; + range_end = entry->addr + entry->size; + /* Out of order E820 maps should not happen: */ + if (range_start < range_end_prev) + pr_info(FW_BUG "out of order E820 entry!\n"); + + if (range_start > range_end_prev) { + pr_info("%s: [gap %#018Lx-%#018Lx]\n", + who, + range_end_prev, + range_start-1); + } + + pr_info("%s: [mem %#018Lx-%#018Lx] ", who, range_start, range_end-1); e820_print_type(entry->type); pr_cont("\n"); + + range_end_prev = range_end; } } -- 2.47.3