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ARAVIND SIVAKUMARAN / FIELD NOTES
Silicon, generated worlds, systems at home.
Notes from a curious engineer.
I write to understand what happens underneath. Start with device memory, explore my anime-generation research, or follow a system from idea to experiment.
Three constellations, linked lessons and independent example runs. PCIe is a branching tree, the IOMMU is stacked translation layers, and power is a cycle of states. Pick a way through: the numbered stars form a route, with each border introducing a new system idea. Choose another route, or press the chosen one again to list all three; without JavaScript all three lists remain available. Or follow one card through all three in a combined lab. New to confidential computing? Start with The Vault.
Teaches A real N100’s PCIe tree, part by part. Needs Nothing. Try Light the route a write takes to memory.
Teaches Bus numbers, windows, and what every port on the path must support. Needs Reading lspci. Try Turn AtomicOps on and find the port that refuses.
Teaches What lspci -vvv says about a card, field by field. Needs Nothing. Try Flip a bit with setpci and read it back.
Teaches The switches that make a device an IOMMU client. Needs Reading lspci. Try Enable PASID and watch what lspci prints.
Teaches One NIC split between two VMs, broken three ways. Needs PASID, ATS & SR-IOV. Try Revoke one tenant’s mapping and watch only it fault.
Teaches BusMaster, the DMA mask and the mapping a write needs. Needs Nothing. Try Change one condition and see what stops the write.
Teaches A teaching example of a DMA write, followed from device to memory. Needs Nothing. Try Step through the write, then break its mapping.
Teaches What the device actually sent, and who it said it was. Needs IOMMU foundations. Try Pick a test recipe and predict its evidence.
Teaches The tables that decide each request, and how a test proves them. Needs A basic DMA example. Try Run an allowed control and a denied probe.
Teaches A page walk, level by level, with 4 KiB, 2 MiB and 1 GiB leaves. Needs IOMMU foundations. Try Trace a request to memory, or to a fault.
Teaches Why a request can succeed on the wrong page. Needs IOMMU foundations. Try Skip an invalidation and follow the bytes.
Teaches Alignment, lookup structures, command completion and GA records. Needs IOMMU foundations. Try Connect a field to the working lab.
Teaches Presence, permissions, invalid encodings and stopped engines. Needs IOMMU foundations. Try Break one assumption and test the recovery.
Teaches SEV-SNP on: RMP checks and RMP_PAGE_FAULT, bit by bit. Needs Confidential VMs. Try Let a device reach for private memory.
Teaches SEV-SNP’s Reverse Map Table, page validation and privilege levels. Needs IOMMU foundations. Try Write a secret, then let the host try.
Teaches Choosing how fast to run while there is work. Needs Nothing. Try Lab PM-01: energy per completed job.
Teaches Idle depth against wake latency. Needs Active. Try Lab PM-02: earn an idle state.
Teaches A device suspending and waking correctly (system sleep itself is reference only). Needs Idle. Try Lab PM-05: suspend, wake, and verify the device.
Teaches CPU, device and link idle before following wake. Needs No earlier Idle chapter. Try Compare safe return paths.
Teaches ASPM and link states: watts against latency. Needs Reading lspci. Try Lab PM-04: link and package dependencies.
These linked lessons use independent examples to introduce PCIe, DMA, translation, faults and power.
For practitioners: go straight to the fields, formats and corner cases.
How I validate: separate what was intended, what was observed and what proves it.
Read and run the browser examples locally. When you choose Run C++ externally, only that experiment’s source is sent to Compiler Explorer. No GPU is required for these IOMMU notes.
PROJECT STUDY / GENERATIVE AI
I trained a 512 × 512 anime StyleGAN2 model. The project connects dataset curation, training choices and the details that still go wrong.
Read the full project study Try the recovered model