[Deepin-Kernel-SIG] [linux 6.6.y] [zhaoxin] x86/microcode/zhaoxin: Fix NULL check for the P4D page allocation x86/mce/zhaoxin: Fix bus number shift in ZDI error reporting

[opsiff]

x86/mce/zhaoxin: Fix bus number shift in ZDI error reporting
x86/microcode/zhaoxin: Fix NULL check for the P4D page allocation

Summary by Sourcery

Fix Zhaoxin-specific x86 error handling and microcode page allocation issues.

Bug Fixes:

• Correct the bit shift used when encoding the bus number in ZDI machine check error reporting.
• Fix the NULL pointer check after allocating the P4D microcode page when 5-level paging is enabled.

[sourcery-ai]

Reviewer's guide (collapsed on small PRs)

Reviewer's Guide

Fixes two Zhaoxin x86 issues: corrects the bit shift used for encoding the bus number in ZDI error reporting, and fixes a NULL pointer check after allocating the P4D page for microcode page tables.

Flow diagram for init_microcode_pages P4D allocation and NULL check

flowchart TD
  A[init_microcode_pages] --> B[pgtable_l5_enabled]
  B -->|false| G[continue without P4D]
  B -->|true| C[microcode_p4d_page = __get_free_page]
  C --> D{microcode_p4d_page is NULL}
  D -->|true| E[pr_err Failed to allocate P4D page]
  E --> F[goto fail_pud]
  D -->|false| H[proceed with microcode P4D setup]

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File-Level Changes

Change	Details	Files
Correct bus number bit placement in ZDI machine-check error reporting for Zhaoxin CPUs.	Adjust the bit shift direction when encoding the high byte of requestor_id into the m.misc field. Ensure the upper bus bits are left-shifted into the correct high-order bits rather than being right-shifted out of range.	arch/x86/kernel/cpu/mce/apei.c
Fix incorrect NULL check after P4D page allocation in Zhaoxin microcode initialization.	Update the post-allocation NULL check to validate microcode_p4d_page instead of microcode_pud_page. Keep failure handling and logging paths the same, only correcting which pointer is checked.	arch/x86/kernel/cpu/microcode/zhaoxin.c

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[deepin-ci-robot]

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[sourcery-ai]

Hey - I've left some high level feedback:

• In zx_apei_mce_report_zdi_error, consider replacing the hard-coded bit positions (19 and 24) with named constants or macros that document the layout of the misc field for ZDI errors, making future maintenance less error-prone.
• In init_microcode_pages, the error path label fail_pud is now used for a P4D allocation failure as well; renaming or restructuring the labels to more clearly reflect the failing allocation step would improve readability of the error handling.

Prompt for AI Agents

Please address the comments from this code review:

## Overall Comments
- In `zx_apei_mce_report_zdi_error`, consider replacing the hard-coded bit positions (19 and 24) with named constants or macros that document the layout of the `misc` field for ZDI errors, making future maintenance less error-prone.
- In `init_microcode_pages`, the error path label `fail_pud` is now used for a P4D allocation failure as well; renaming or restructuring the labels to more clearly reflect the failing allocation step would improve readability of the error handling.

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[Copilot]

Pull request overview

Fixes two Zhaoxin-specific x86 issues: one in early microcode page-table setup when 5-level paging is enabled, and one in ZDI machine-check error encoding for APEI reporting.

Changes:

• Correct the NULL check to validate the newly allocated P4D page (instead of mistakenly checking the PUD page).
• Fix bus number encoding by shifting the extracted requestor bus byte into the correct bit position in m.misc.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
arch/x86/kernel/cpu/microcode/zhaoxin.c	Fixes incorrect NULL check after allocating the P4D page during microcode identity-mapping setup under 5-level paging.
arch/x86/kernel/cpu/mce/apei.c	Corrects the bit shift used to pack the requestor bus number into the MCE misc field for ZDI error reporting.

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