Only enforce /boot location limit on non-EFI systems (#2391443)

[vojtechtrefny]

We currently require the /boot partition to be placed in a way the last sector is under 2 TiB. This is an old check that predates EFI and GPT and should not apply on these systems.

Summary by Sourcery

Bug Fixes:

• Avoid incorrectly enforcing the 2 TiB /boot location limit on EFI systems that do not have this constraint.

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Skips the legacy 2 TiB end-sector constraint for /boot partition placement when running on EFI systems, while preserving the limit on non-EFI systems.

Flow diagram for applying /boot 2_TiB limit based on EFI detection

flowchart TD
    A[get_best_free_space_region called] --> B[Is /boot partition requested? boot flag]
    B -- No --> C[Skip /boot size constraint]
    C --> D[Evaluate free space region normally]

    B -- Yes --> E[Call is_efi]
    E -- System is EFI --> F[Do not enforce 2_TiB /boot end-sector limit]
    F --> D

    E -- System is not EFI --> G[Set max_boot to 2_TiB]
    G --> H[Compute free_start from free_geom and sectorSize]
    H --> I[Compute req_end as free_start + req_size]
    I --> J[Check that req_end <= max_boot]
    J --> K[If req_end exceeds max_boot, reject this free space region]
    K --> D

Loading

File-Level Changes

Change	Details	Files
Conditionally apply the 2 TiB /boot partition end-sector limit only on non-EFI systems.	Import EFI detection helper to check whether the system is EFI-based. Update the boot-partition placement logic to bypass the 2 TiB constraint when EFI is detected, keeping existing behavior for non-EFI systems.	blivet/partitioning.py

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[sourcery-ai]

Hey there - I've reviewed your changes - here's some feedback:

• Using is_efi() here ties the /boot constraint to the environment where blivet runs rather than the target system; if this code can operate on non-local/alternate targets (e.g., image creation, chroot installs), consider plumbing a target-boot-mode flag into get_best_free_space_region instead of calling is_efi() directly.
• It might be helpful to add a brief code comment explaining why the 2 TiB limit is skipped on EFI (i.e., historical BIOS/MBR constraint) so future readers don’t reintroduce or refactor this check without understanding the context.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- Using `is_efi()` here ties the /boot constraint to the environment where blivet runs rather than the target system; if this code can operate on non-local/alternate targets (e.g., image creation, chroot installs), consider plumbing a target-boot-mode flag into `get_best_free_space_region` instead of calling `is_efi()` directly.
- It might be helpful to add a brief code comment explaining why the 2 TiB limit is skipped on EFI (i.e., historical BIOS/MBR constraint) so future readers don’t reintroduce or refactor this check without understanding the context.

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