[Deepin-Kernel-SIG] [linux 6.6.y] [Upstream] KVM: x86/mmu: Check write tracking in all address spaces

[opsiff]

stable 6.6.156 #2120

use mainline version.

kvm_gfn_is_write_tracked() checks only the supplied memslot, but page tracking is per-address-space and shadow pages are shared across all address spaces. With SMM, a GFN can therefore be write-tracked in one address space and appear untracked through the other.

Check the supplied slot first, then the slot for the other address space. This ensures all callers honor write tracking regardless of the active address space. In particular, it prevents mmu_try_to_unsync_pages() from marking an upper-level shadow page unsync and eventually triggering the BUG in pte_list_remove().

Fixes: 699023e ("KVM: x86: add SMM to the MMU role, support SMRAM address space")
Assisted-by: Codex:GPT-5

Message-ID: 20260721103512.2136240-2-kimjw04271234@gmail.com
[invert direction of the conditional. - Paolo]

(cherry picked from commit 0f38453)

Summary by Sourcery

Fix KVM x86 write-tracking checks so shared shadow pages honor tracking state across address spaces.

Bug Fixes:

• Ensure KVM x86 write tracking is recognized across all address spaces, preventing incorrect shadow-page synchronization and potential MMU crashes when using SMM.

Enhancements:

• Refactor write-tracking checks to evaluate both the supplied memory slot and its corresponding slot in the alternate address space.

[sourcery-ai]

Reviewer's Guide

Updates KVM x86 write-tracking detection to search both address spaces, preventing SMM-related mismatches where shared shadow pages could be treated as untracked and later trigger pte_list_remove() failures.

Flow diagram for KVM write-tracking lookup across address spaces

flowchart TD
    A[kvm_gfn_is_write_tracked] --> B{Write tracking enabled?}
    B -- No --> C[Return false]
    B -- Yes --> D[Check supplied memslot]
    D -- Tracked --> E[Return true]
    D -- Untracked --> F{Second address space exists?}
    F -- No --> G[Return false]
    F -- Yes --> H[Find other address-space memslot]
    H --> I[Check other memslot]
    I -- Tracked --> E
    I -- Untracked --> G

Loading

File-Level Changes

Change	Details	Files
Make write-tracking checks account for both KVM address spaces while preserving the existing fast path for the supplied slot.	Extract per-slot write-tracking lookup into a null-safe helper. Check the supplied memory slot first, then resolve and check the corresponding slot in the alternate address space. Add a build-time constraint for the two-address-space XOR lookup and retain early exits when tracking is disabled or no slot is supplied.	arch/x86/kvm/mmu/page_track.c

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