refactor: de-duplicate virtio queue validation logic #5276
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Just call initialize() again. It does some needless alignment checking, but that's not really harmful. Signed-off-by: Patrick Roy <[email protected]>
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## main #5276 +/- ##
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+ Coverage 82.83% 82.91% +0.08%
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Files 250 250
Lines 26968 26902 -66
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+ Misses 4630 4596 -34
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Factor out the alignment checks on the vring components into get_slice_ptr, instead of writing them out 3 times in initialize(). While we're at it, also explain why its okay to only alignment check the GPA and not the HVAs as well. Signed-off-by: Patrick Roy <[email protected]>
Vring validation was a bit awkwardly split across two functions which did overlapping sets of checks: Queue::initialize verified alignment and memory accesses, while Queue::is_valid additionally checked Queue::ready and Queue::size. However, on the activation path, both were called, meanign we checked alignment twice (.initialize() is called in .activate(), but we only call .activate() if .is_valid() returned true). This is confusing at best, and at worst made us potentially virtio spec incompliant: If the quest tried to activate a virtio device, but this failed because some vring was not valid (in terms of Queue::is_valid), then Firecracker would silently ignore the activation request. Now, it instead marks the device as needing reset, and notifies the guest of its failure to properly configure the vrings. While we're at it, also remove some duplicated checks from the vring restoration code: .initialize() is called for activated devices, so there's no need to later validate the size specifically again, and also no need for the additional call to is_valid(). Fix up some unit tests that activate virtio devices where some queues do not satisfy the old Queue::is_valid() checks, as now these checks must pass for activation to succeed. The only interesting fix here is in test_virtiodev_sanity_checks in virtio/persist.rs, which can be seen as a symptom of a bug fix: Previously, restoration code refused to load snapshots that had their queue size set to a value larger than Queue::max_size, even if a device was not activated. This is arguably wrong, as The guest can configure a queue to have a size greater than max size no problem, and never activate the device for example, in which case prior to this commit Firecracker would refuse to resume snapshots taken of such VMs. Signed-off-by: Patrick Roy <[email protected]>
verify_size only had assertions about our mocks, which is not very useful (in fact, the second assertion was trivially true, no matter what we did). So let's just remove it. Signed-off-by: Patrick Roy <[email protected]>
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ShadowCurse
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Jun 23, 2025
Manciukic
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As part of #5260 we noticed that parts of our virtio queue validation logic was duplicated between
Queue::is_validandQueue::initialize, resulting in most queue invariants being checked twice needlessly. This PR fixed this by merging the two functions, and having all validation happen right before activation (refusing to activate the device if validation of any of its queues fails).License Acceptance
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Certificate of Origin and signing off your commits, please check
CONTRIBUTING.md.PR Checklist
tools/devtool checkstyleto verify that the PR passes theautomated style checks.
how they are solving the problem in a clear and encompassing way.
in the PR.
CHANGELOG.md.Runbook for Firecracker API changes.
integration tests.
TODO.rust-vmm.