Have Firecracker tell UFFD handler about page size during initial handshake #4449
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Additional details and impacted files@@ Coverage Diff @@
## main #4449 +/- ##
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+ Coverage 81.37% 81.56% +0.18%
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Files 243 243
Lines 29518 29542 +24
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+ Hits 24021 24095 +74
+ Misses 5497 5447 -50
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ShadowCurse
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Feb 14, 2024
When using a page-size agnostic UFFD handler, orchestration becomes easier if Firecracker tells the UFFD handler about page size (instead of some orchestrator having to tell both Firecracker and the UFFD handler about the page size independently). Thus, send along the page size in the initial payload that Firecracker sends to the UFFD handler (e.g. the one also containing information about the memory regions). We send the page size information for each region (even though Firecracker does not support per-region configuration of huge pages) for backward compatibility reasons (changing the top-level json object from a list of region to a dictionary would be a breaking change, but adding a field to each list entry is not). Signed-off-by: Patrick Roy <roypat@amazon.co.uk>
Document the new part of the initial handshake where Firecracker tells the UFFD handler about page size in KiB. Signed-off-by: Patrick Roy <roypat@amazon.co.uk>
Have the examples and tests utilize the page size information that Firecracker sends as part of the initial UFFD payload. This allows us to get rid of the separate uffd handler examples for the 4K and 2M test cases. Signed-off-by: Patrick Roy <roypat@amazon.co.uk>
Factor out the parts of the function that do not require holding a valid UFFD object into their own functions for which we can then write unittests. Also write the unittests. Signed-off-by: Patrick Roy <roypat@amazon.co.uk>
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LGTM, we agreed to run a little bit of the tests manually to make sure https://buildkite.com/firecracker/firecracker-pr/builds/9088#018dac2d-4b95-4b19-a327-a59ddee918e2 is a spurious failure not caused by the content of the PR.
ShadowCurse
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We managed to reproduce this intermittent failure on the |
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This will make orchestration easier, as the whatever spawns the Firecracker and UFFD handler processes now does not have to ensure both get the passed the same hugepages configuration (and it also simplifies our testing setup)
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