CVS commit: src/sys/arch

["Pierre Pronchery" <khorben%netbsd.org@localhost>]

Module Name:    src
Committed By:   khorben
Date:           Fri Dec  5 17:58:12 UTC 2025

Modified Files:
        src/sys/arch/amd64/amd64: genassym.cf locore.S
        src/sys/arch/amd64/conf: MICROVM
        src/sys/arch/x86/x86: x86_machdep.c

Log Message:
sys/arch/amd64: support ramdisks when booting in GENPVH mode

This adds support for booting NetBSD/amd64 with QEMU’s -kernel/-initrd
combination, in generic PVH mode (GENPVH). This includes the MICROVM
kernel, which now defaults to supporting modules and root on memory
disks.

This patch probes the first few bytes loaded in memory for
differentiating between modules, splash screens (PNG or JPEG), or
assumes filesystem images otherwise. It works with plain filesystem
images, but not with modules yet. Supporting any combination of
filesystem, modules or splash screen images should be possible in the
future.

Tested on NetBSD/amd64 by iMil and myself; measured to gain another 1~3
ms of boot time with the MICROVM kernel on the reference hardware.

As posted on tech-kern@ on 26/11/2025, with no objections.

XXX pull-up to -11 and adapt for -10


To generate a diff of this commit:
cvs rdiff -u -r1.99 -r1.100 src/sys/arch/amd64/amd64/genassym.cf
cvs rdiff -u -r1.233 -r1.234 src/sys/arch/amd64/amd64/locore.S
cvs rdiff -u -r1.4 -r1.5 src/sys/arch/amd64/conf/MICROVM
cvs rdiff -u -r1.159 -r1.160 src/sys/arch/x86/x86/x86_machdep.c

Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.