[virtio-mem] Fuzzer and integ tests fixes #5521
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Additional details and impacted files@@ Coverage Diff @@ ## feature/virtio-mem #5521 +/- ## ====================================================== - Coverage 83.34% 83.32% -0.03% ====================================================== Files 276 276 Lines 28810 28823 +13 ====================================================== + Hits 24012 24017 +5 - Misses 4798 4806 +8
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Manciukic added the Status: Awaiting review Manciukic force-pushed the feature/virtio-mem branch from fd76154 to 0c156c4 Compare When the fuzzer generates an invalid bitvec state, the serde code crashes with an assertion error. To avoid these crashes, just store it as a plain Vec<bool> as we don't expect these vecs to be too big (for a 10GB hotpluggable area with 2MiB blocks it would require 5kB for the Vec<bool> compared to 640B with BitVec). Signed-off-by: Riccardo Mancini <mancio@amazon.com>
Return the error up the stack instead of unwrapping it. Note that on PCI this error is unwrapped for every device so there's no change there. Signed-off-by: Riccardo Mancini <mancio@amazon.com>
When the region state is invalid or corrupted (like when generated by the fuzzer), it is possible that a DRAM slot is unplugged, leading to segfaults when accessing guest memory (ie from vmgenid device). To avoid these crashes, validate the region state and allow the DRAM region (not hot-pluggable) to only contain one plugged slot. Signed-off-by: Riccardo Mancini <mancio@amazon.com>
Sometimes on m6a the uffd test fails to write 1.2GB within 10s. Bump the timeout to 30s. Signed-off-by: Riccardo Mancini <mancio@amazon.com>
Manciukic force-pushed the virtio-mem/fix-fuzzer branch from 1cab5f6 to 19fc136 Compare The previously set 256MB were not enough for hotplugging 16GB of memory. This is because the kernel needs 64B for every 4kB page, meaning 262MB for 16GB. Signed-off-by: Riccardo Mancini <mancio@amazon.com>
Manciukic force-pushed the virtio-mem/fix-fuzzer branch from 379c645 to e5f6dc9 Compare 
ShadowCurse approved these changes Nov 20, 2025
Manciukic changed the title 
bchalios reviewed Nov 21, 2025
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bchalios left a comment
bchalios left a comment There was a problem hiding this comment.
Generally LGTM.
However, it's very annoying that we need to change a type because fuzzer isn't able to create a valid object. Isn't there a way we could skip fuzzer runs that create invalid BitVec objects?
bchalios approved these changes Nov 21, 2025
Manciukic merged commit c37849c into firecracker-microvm:feature/virtio-mem 6 of 7 checks passed
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Changes
Fuzzer fixes:
bitvectoVec<bool>to persist to avoid crashes on restore of malformed snapshotInteg test fixes:
Reason
Fix crashes detected by the fuzzer.
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integration tests.
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