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kernel: load at 16 MB, clear of what firmware keeps low

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From 1 MB the 34 MB kernel ran across 8 MB, where OVMF keeps ACPI NVS
memory that outlives the firmware -- so it was overwritten on every
boot, after ExitBootServices. Firmware leaves its leftovers low; above
16 MB is where a machine is most reliably empty.

KERNPHYS in memlayout.h, and kernel.ld agreeing with it. Nothing else
named the old address. Under OVMF the range is now only boot-services
memory: staged, copied home after the firmware exits, no warning. Boots
as a CD and as a USB disk, 1 and 4 CPUs.

The 15 MB below the kernel is not given to the page allocator yet.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S1giNvrHTrPMPw7V6x1kQ4
This commit is contained in:
Nexoniarz 2026-10-24 00:13:53 +02:00
commit 5ed8f1b0d5
4 changed files with 14 additions and 5 deletions
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4
kernel/kernel.ld
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@ -7,13 +7,13 @@ OUTPUT_FORMAT("elf64-x86-64")
OUTPUT_ARCH(i386:x86-64)
ENTRY(_start)
mboot_load_addr = 0x00100000;
mboot_load_addr = 0x01000000; /* KERNPHYS in include/arch/memlayout.h */
SECTIONS
{
/* Link the kernel at this address: "." means the current address */
/* Must be equal to KERNLINK */
. = 0xFFFF800000100000;
. = 0xFFFF800001000000;
PROVIDE(begin = .);