fix(mm): add VmIo retry logic for lazy allocation #94
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
When kernel reads/writes user memory that is lazily allocated but not yet faulted in, user_copy (assembly function) uses exception table to handle page faults and returns failure instead of triggering the kernel's page fault handler. Fix: Add retry logic in VmIo read/write: 1. First attempt the read/write via user_copy 2. If failed, calculate the faulting address from failure offset 3. Call populate_area() to ensure pages are allocated 4. Retry the read/write operation Also changed ELF segment mapping to use populate=true for immediate allocation to avoid retry overhead during early execution.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
VmIo Lazy Allocation Failure
Files:
core/src/mm.rsapi/src/io.rsapi/src/mm.rsBug Description:
When the kernel tried to read/write user memory that was lazily allocated but not yet faulted in, the operation would fail with
AccessDeniedinstead of triggering page fault handling.Fix:
Added retry logic with page population:
populate_areato ensure the pages are allocated