[Bug 230172] FreeBSD 11.2 fails to boot on Celeron J1900 after upgrade from 11.1 (ACPI indicates no VGA)

From: <bugzilla-noreply_at_freebsd.org>
Date: Thu, 24 Feb 2022 15:02:23 UTC
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=230172

Ed Maste <emaste@freebsd.org> changed:

           What    |Removed                     |Added
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                 CC|                            |royger@freebsd.org

--- Comment #59 from Ed Maste <emaste@freebsd.org> ---
ACPI FADT VGA check was added in:

commit c2272faa06dec2f027c5359529cf8f4f3593c164
Author: Roger Pau Monné <royger@FreeBSD.org>
Date:   Tue Mar 13 09:38:53 2018 +0000

    vt_vga: check if VGA is available from ACPI FADT table

    On x86 the IA-PC Boot Flags in the FADT can signal whether VGA is
    available or not.

In Linux presence of the the flag sets x86_platform.legacy.no_vga = 1 which is
used in only one place, arch/x86/xen/enlighten_hvm.c xen_hvm_guest_late_init()

In particular as far as I can tell it does not appear to control whether the
VGA console is probed or not. It seems there is a lot of firmware with broken
ACPI tables that incorrectly sets this flag and it may be better to ignore it.
Roger, is it possible that the flag could be used only w/ Xen?

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