ArmPkg/ArmMmuLib AARCH64: Add missing ISB after page table update #4418
Conversation
This file contains 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
The helper that updates live page table entries writes a zero entry, invalidates the covered address range from the TLBs, and finally writes the actual entry. This ensures that no TLB conflicts can occur. Writing the final entry needs to complete before any translations can be performed, as otherwise, the zero entry, which describes an invalid translation, may be observed by the page table walker, resulting in a translation fault. For this reason, the final write is followed by a DSB barrier instruction. However, this barrier will not stall the pipeline, and instruction fetches may still hit this invalid translation, as has been observed and reported by Oliver. To ensure that the new translation is fully active before returning from this helper, we have to insert an ISB barrier as well. Reported-by: Oliver Steffen <osteffen@redhat.com> Tested-by: Oliver Steffen <osteffen@redhat.com> Reviewed-by: Leif Lindholm <quic_llindhol@quicinc.com> Acked-by: Michael D Kinney <michael.d.kinney@intel.com> Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
# for free
to join this conversation on GitHub.
Already have an account?
# to comment
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Outdated suggestions cannot be applied.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.
The helper that updates live page table entries writes a zero entry, invalidates the covered address range from the TLBs, and finally writes the actual entry. This ensures that no TLB conflicts can occur.
Writing the final entry needs to complete before any translations can be performed, as otherwise, the zero entry, which describes an invalid translation, may be observed by the page table walker, resulting in a translation fault. For this reason, the final write is followed by a DSB barrier instruction.
However, this barrier will not stall the pipeline, and instruction fetches may still hit this invalid translation, as has been observed and reported by Oliver. To ensure that the new translation is fully active before returning from this helper, we have to insert an ISB barrier as well.
Reported-by: Oliver Steffen osteffen@redhat.com
Tested-by: Oliver Steffen osteffen@redhat.com
Reviewed-by: Leif Lindholm quic_llindhol@quicinc.com
Acked-by: Michael D Kinney michael.d.kinney@intel.com