So I was looking into a E820 table related bug report by
Paul Menzel, and I wanted to implement the behavior
suggested by the ACPI specification, which bug/problem
results in unbootable Linux systems with certain bootloaders:
https://lore.kernel.org/r/074c2637-1b65-428e-b3e2-24384780e936@molgen.mpg.de
One thing led to another, and now I'm here 29 patches later,
trying to explain what they all do. :-/
In order of importance:
- The bugfix / change of Linux kernel E820 table parsing behavior:
x86/boot/e820: Treat non-type-2 'reserved' E820 region types as E820_TYPE_RESERVED
- A change to e820_search_gap() to fix an implementational oddity
that would prefer lower-address same-size PCI gaps over larger-address
PCI gaps. Now the implementation searches for the largest gap:
x86/boot/e820: Change e820_search_gap() to search for the highest-address PCI gap
- A rewrite of e820_search_gap() to search the E820 table in ascending
order to make sure even weird PCI holes get found, as claimed by the
comments around the code (but not properly implemented):
x86/boot/e820: Make sure e820_search_gap() finds all gaps
- Remove the exclusion of single-entry E820 tables passed in by
firmware:
x86/boot/e820: Simplify append_e820_table() and remove restriction on single-entry tables
- A debuggability improvement, to print the sizes of the e820 entries
and the holes as well, because parsing raw hexadecimal ranges is hard
for humans:
x86/boot/e820: Print gaps in the E820 table
x86/boot/e820: Print out sizes of E820 memory ranges
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] 639 KB kernel usable RAM
BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] 1 KB device reserved
BIOS-e820: [gap 0x00000000000a0000-0x00000000000effff] 320 KB ...
BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] 64 KB device reserved
BIOS-e820: [mem 0x0000000000100000-0x000000007ffdbfff] 1.9 GB kernel usable RAM
BIOS-e820: [mem 0x000000007ffdc000-0x000000007fffffff] 144 KB device reserved
BIOS-e820: [gap 0x0000000080000000-0x00000000afffffff] 768 MB ...
BIOS-e820: [mem 0x00000000b0000000-0x00000000bfffffff] 256 MB device reserved
BIOS-e820: [gap 0x00000000c0000000-0x00000000fed1bfff] 1005.1 MB ...
BIOS-e820: [mem 0x00000000fed1c000-0x00000000fed1ffff] 16 KB device reserved
BIOS-e820: [gap 0x00000000fed20000-0x00000000feffbfff] 2.8 MB ...
BIOS-e820: [mem 0x00000000feffc000-0x00000000feffffff] 16 KB device reserved
BIOS-e820: [gap 0x00000000ff000000-0x00000000fffbffff] 15.7 MB ...
BIOS-e820: [mem 0x00000000fffc0000-0x00000000ffffffff] 256 KB device reserved
BIOS-e820: [gap 0x0000000100000000-0x000000fcffffffff] 1008 GB ...
BIOS-e820: [mem 0x000000fd00000000-0x000000ffffffffff] 12 GB device reserved
Note how weirdly broken up ranges are printed with fractional size
values, while 'round' ranges are printed as natural numbers.
- Assorted cleanups: type cleanups, simplifications, standardization
of coding patterns, etc.
The tree can be found in the WIP.x86/e820 branch of the mingo/tip.git tree:
git://git.kernel.org/pub/scm/linux/kernel/git/mingo/tip.git WIP.x86/e820
It's lightly tested at the moment.
Thanks,
Ingo
===============>
Ingo Molnar (29):
x86/boot/e820: Remove inverted boolean logic from the e820_nomerge() function name, rename it to e820_type_mergeable()
x86/boot/e820: Simplify e820__print_table() a bit
x86/boot/e820: Simplify the PPro Erratum #50 workaround
x86/boot/e820: Mark e820__print_table() static
x86/boot/e820: Print gaps in the E820 table
x86/boot/e820: Make the field separator space character part of e820_print_type()
x86/boot/e820: Print out sizes of E820 memory ranges
x86/boot/e820: Print E820_TYPE_RAM entries as ... RAM entries
x86/boot/e820: Call the PCI gap a 'gap' in the boot log printout
x86/boot/e820: Use 'u64' consistently instead of 'unsigned long long'
x86/boot/e820: Remove pointless early_panic() indirection
x86/boot/e820: Clean up confusing and self-contradictory verbiage around E820 related resource allocations
x86/boot/e820: Improve e820_print_type() messages
x86/boot/e820: Clean up __e820__range_add() a bit
x86/boot/e820: Clean up __refdata use a bit
x86/boot/e820: Remove unnecessary header inclusions
x86/boot/e820: Standardize e820 table index variable names under 'idx'
x86/boot/e820: Change struct e820_table::nr_entries type from __u32 to u32
x86/boot/e820: Standardize e820 table index variable types under 'u32'
x86/boot/e820: Clean up e820__setup_pci_gap()/e820_search_gap() a bit
x86/boot/e820: Change e820_search_gap() to search for the highest-address PCI gap
x86/boot/e820: Rename gap_start/gap_size to max_gap_start/max_gap_start in e820_search_gap() et al
x86/boot/e820: Simplify & clarify __e820__range_add() a bit
x86/boot/e820: Standardize __init/__initdata tag placement
x86/boot/e820: Simplify append_e820_table() and remove restriction on single-entry tables
x86/boot/e820: Remove e820__range_remove()'s unused return parameter
x86/boot/e820: Simplify the e820__range_remove() API
x86/boot/e820: Make sure e820_search_gap() finds all gaps
x86/boot/e820: Treat non-type-2 'reserved' E820 region types as E820_TYPE_RESERVED
arch/x86/include/asm/e820/api.h | 3 +-
arch/x86/include/asm/e820/types.h | 2 +-
arch/x86/kernel/e820.c | 518 ++++++++++++++++++++++----------------
arch/x86/kernel/setup.c | 10 +-
arch/x86/platform/efi/efi.c | 3 +-
5 files changed, 307 insertions(+), 229 deletions(-)
--
2.45.2