Add terminology and boundaries RFC by moosingin3space · Pull Request #2 · nebulet/rfcs

moosingin3space · 2018-10-12T04:56:03Z

lachlansneff

Just a few questions and notes.

lachlansneff · 2018-10-12T14:06:23Z

text/0000-terminology-and-boundaries.md

+proposes we define the following terms to refer to parts of our OS, adapted
+from [EROS](https://web.archive.org/web/20160412201504/http://www.coyotos.org/docs/misc/eros-structure.pdf):
+the _kernel_, which implements threading and inter-proces communication (IPC)
+as a wasm module, the _nucleus_, which implements a small wasm JIT natively,


Just to be clear, the kernel will be a wasm module that runs on the nucleus?

Yes, this has been clarified in my latest revision.

lachlansneff · 2018-10-12T14:07:42Z

text/0000-terminology-and-boundaries.md

+from [EROS](https://web.archive.org/web/20160412201504/http://www.coyotos.org/docs/misc/eros-structure.pdf):
+the _kernel_, which implements threading and inter-proces communication (IPC)
+as a wasm module, the _nucleus_, which implements a small wasm JIT natively,
+and the _firmament_, which specifies IPC interfaces for drivers to implement.


Is the firmament an actual "thing", or just a way to define interfaces between drivers and processes?

The firmament would be the equivalent of the syscall boundary in a traditional OS.

Sounds good.

lachlansneff · 2018-10-12T14:08:24Z

text/0000-terminology-and-boundaries.md

+  RFCs.
+- The _nucleus_, which implements a small WebAssembly runtime in native code. A
+  nucleus will implement the minimal set of hardware interfaces required by the
+  kernel and will likely resemble an exokernel on its surface. A nucleus need not


Good call about the exokernel-like interface

lachlansneff · 2018-10-12T14:08:50Z

text/0000-terminology-and-boundaries.md

+The Nebulet operating system architecture is defined in terms of four
+components:
+
+- The _kernel_, which implements the core functionality of a microkernel OS:


Can you be clearer about whether the kernel is a wasm module or not?

Done in latest commit.

lachlansneff · 2018-10-12T14:13:13Z

text/0000-terminology-and-boundaries.md

+
+interface EthernetNic {
+    fn send(&mut self, pkt: EthernetPacket) -> Result<()>;
+    fn send_inplace(&mut self, func: impl Fn(&mut EthernetPacket) -> Result<()>) -> Result<()>;


I'm curious how send_inplace would work. The user supplies it a function that takes a EthernetPacket reference?

See link for an example of a similar function. The idea here is that the network driver can allocate a packet located inside its Tx queue, then the application modifies the packet.
https://github.com/libpnet/libpnet/blob/master/pnet_datalink/src/linux.rs#L231

Oh interesting! I hadn't thought of that. It'd be difficult to get the packet into the other wasm linear memory without copying, but could be possible through page flipping.

lachlansneff · 2018-10-12T14:15:08Z

text/0000-terminology-and-boundaries.md

+# Drawbacks
+[drawbacks]: #drawbacks
+
+Implementing all drivers as WebAssembly applications may not be able to provide


This is an important thing to think about. I'm leaning towards being able to dynamically load (or at startup only, depending on the security model) clif ir for drivers without sandboxing overhead, but this remains to be seen.

As someone with both a security and networking background, I would argue in favor of statically-compiled drivers, with the nucleus implementing the firmament. That said, I wonder if we can somehow have it both ways.

Okay, I'm okay with that. I suppose recompiling the nucleus for each different use-case is fine.

lachlansneff · 2018-10-12T14:16:57Z

text/0000-terminology-and-boundaries.md

+  thread/process scheduling and isolation, and inter-process communication
+  (IPC). These two pieces of functionality will be further specified in future
+  RFCs.
+- The _nucleus_, which implements a small WebAssembly runtime in native code. A


If the nucleus is to contain the webassembly compiler and runtime, which are largely architecture independent, should we break it up further? That is, into the compiler/runtime and the HAL?

Good idea. Another boundary, yay!

lachlansneff · 2018-10-15T04:15:20Z

Thinking about it again, I'm attempting to figure out how we'd implement a microkernel in wasm. So, obviously, it would use the nucleus' hal interface and whatnot, but still. Where is that line drawn? I think it's a good idea to split up the components, but the kernel should be native.

lachlansneff reviewed Oct 12, 2018

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lachlansneff self-assigned this Oct 12, 2018

lachlansneff added the design label Oct 12, 2018

moosingin3space force-pushed the master branch from 5a9685b to 0fa154f Compare October 13, 2018 05:52

Add terminology and boundaries RFC

5e8df78

moosingin3space force-pushed the master branch from 0fa154f to 5e8df78 Compare October 20, 2018 19:37

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lachlansneff commented Oct 15, 2018

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moosingin3space commented Oct 12, 2018 •

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