[Bug 233211] [boot] [image] 11.2-RELEASE freezes Gigabyte motherboard

[bugzilla-noreply at freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=233211

            Bug ID: 233211
           Summary: [boot] [image] 11.2-RELEASE freezes Gigabyte
                    motherboard
           Product: Base System
           Version: 11.2-RELEASE
          Hardware: amd64
                OS: Any
            Status: New
          Keywords: crash, easy, install, standards
          Severity: Affects Some People
          Priority: ---
         Component: standards
          Assignee: standards at FreeBSD.org
          Reporter: rodrigo.freebsd at minasambiente.com.br
                CC: bcran at FreeBSD.org, kevans at freebsd.org

OVERVIEW:
FreeBSD-11.2-RELEASE-amd64-memstick.img causes computer to freeze until
rearranging installation media MBR and partition alignment on Gygabyte
motherboard GA-G41M-ES2L

STEPS TO REPRODUCE:
Using various USB sticks with various different BIOS configurations (USB
1.0/2.0 Enable/Disable | Legacy USB Support Enable/Disable etc), tested with 6
different vendor/sizes USB sticks with same result: Computer freezes right
after BIOS memory check at initial stages. Same USB sticks works if loaded with
different content (e.g. GRUB from other OSes).

STEPS TO FIX THE ISSUE:
It seems that realigning the partitions to MiB boundaries fixed the freezing
issue. The original FreeBSD-11.2-RELEASE-amd64-memstick has the EFI partition
starting at sector 1, right after MBR data.

The following steps resulted in a fix for the situation:
- Backing up MBR, EFI and BOOT partitions from actual USB stick loaded with the
image.
- Wipe USB stick with zeros
- Restore MBR from backup
- Delete actual partitions as pointed in MBR using fdisk on linux
- Recreate the EFI and BOOT partitions using linux fdisk with exact same total
sector size as in the original image and same partition ID types
- Restoring EFI and BOOT partition data from backup to the newly created ones

After this procedure the EFI partition starts at sector 2048 and no more at
sector 1. Now aligned to MiB as this is a standard in recent linux fdisk
program

CONSIDERATIONS:
Although I’m not an expert in the subject what I think is (and I may be wrong
on these):
- The EFI partition starting at sector 1 seems like an exotic alignment (or not
really aligned to expected usual page sizes)
- Using usual/recommended partition alignment can avoid compatibility issues by
avoiding uncommon situations (not tested at product development cycle, e.g.
tested only with expected page sizes or even hardware being unable to load very
different page sizes from BIOS)
- Sector 1 is expected to be used by GPT in GPT scheme, keeping that space free
of use for other purposes seems to be a good call, for compatibility reasons.

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