vmm: open backing file read-only when not shared#7674
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rbradford merged 1 commit intocloud-hypervisor:mainfrom Feb 6, 2026
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vmm: open backing file read-only when not shared#7674rbradford merged 1 commit intocloud-hypervisor:mainfrom
rbradford merged 1 commit intocloud-hypervisor:mainfrom
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When restoring from snapshot with shared=false, write access to the backing file is not required. Opening it read-only allows restore to succeed on read-only media and overlay lower layers while preserving MAP_PRIVATE semantics. Signed-off-by: Rowen-Ye <rowenye1@gmail.com>
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When restoring a VM from snapshot with a backing_file and shared=false, the code still opens the file read‑write.
This unnecessarily requires write permission even though the mapping is MAP_PRIVATE and does not persist changes to disk.
This becomes a blocker for common read‑only workflows, such as:
For shared=false, the backing file is now opened read‑only, which:
Signed-off-by: Rowen-Ye rowenye1@gmail.com