[v1.14] Expose memory mapping & dirty pages; Make memfile dump optional#8
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bchalios wants to merge 6 commits intofirecracker-v1.14from
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[v1.14] Expose memory mapping & dirty pages; Make memfile dump optional#8bchalios wants to merge 6 commits intofirecracker-v1.14from
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February 12, 2026 10:24
Add a few APIs to get information about guest memory: * An endpoint for guest memory mappings (guest physical to host virtual). * An endpoint for resident and empty pages. * An endpoint for dirty pages. Signed-off-by: Babis Chalios <babis.chalios@e2b.dev>
There are cases where a user might want to snapshot the memoyr of a VM externally. In these cases, we can ask Firecracker to avoid serializing the memory file to disk when we create a snapshot. Signed-off-by: Babis Chalios <babis.chalios@e2b.dev>
Implement API /memory/mappings which returns the memory mappings of guest physical to host virtual memory. Signed-off-by: Babis Chalios <babis.chalios@e2b.dev>
Implement API /memory which returns two bitmaps: resident and empty. `resident` tracks whether a guest page is in the resident set and `empty` tracks whether it's actually all 0s. Both bitmaps are structures as vectors of u64, so their length is: total_number_of_pages.div_ceil(64). Pages are ordered in the order of pages as reported by/memory/mappings. Signed-off-by: Babis Chalios <babis.chalios@e2b.dev>
Implement API /memory/dirty which returns a bitmap tracking dirty guest memory. The bitmap is structured as a vector of u64, so its length is: total_number_of_pages.div_ceil(64). Pages are ordered in the order of pages as reported by /memory/mappings. Signed-off-by: Babis Chalios <babis.chalios@e2b.dev>
UFFD provides an API to enable write-protection for memory ranges tracked by a userfault file descriptor. Detailed information can be found here: https://docs.kernel.org/admin-guide/mm/userfaultfd.html. To use the feature, users need to register the memory region with UFFDIO_REGISTER_MODE_WP. Then, users need to enable explicitly write-protection for sub-ranges of the registered region. Writes in pages within write-protected memory ranges can be handled in one of two ways. In synchronous mode, writes in a protected page will cause kernel to send a write protection event over the userfaultfd. In asynchronous mode, the kernel will automatically handle writes to protected pages by clearing the write-protection bit. Userspace can later observe the write protection bit by looking into the corresponding entry of /proc/<pid>/pagemap. This commit, uncoditionally, enables write protection for guest memory using the asynchronous mode. !NOTE!: asynchronous write protection requires (host) kernel version 6.7 or later). Signed-off-by: Babis Chalios <babis.chalios@e2b.dev>
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| impl PagemapReader { | ||
| /// Create a new PagemapReader | ||
| pub fn new(_page_size: usize) -> Result<Self, PagemapError> { | ||
| let pagemap_fd = File::open("/proc/self/pagemap").map_err(PagemapError::OpenPagemap)?; |
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CONTRIBUTING.md.PR Checklist
tools/devtool checkbuild --allto verify that the PR passesbuild checks on all supported architectures.
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.