Leinux tristone13th

When does Linux KVM emulate instructions?

Flow Chart

graph LR

x86_emulate_instruction --> x86_emulate_insn
emulate_instruction --> x86_emulate_instruction

vsock notes

about vsocks

Vsocks are a means of providing socket communication (either stream or datagram) directly between VMs and their host operating system. The host and each VM have a 32 bit CID (Context IDentifier) and may connect or bind to a 32 bit port number. Ports < 1024 are privileged ports.

Vsock communication between VMs does not seem to work.
Only one vsock device per VM is supported.

Seamlessly editing remote files in (Neo)Vim with Netrw and scp

Neovim and Vim both come bundled with a standard plugin called Netrw. Netrw acts a file explorer (similar to NERDTree), but more importantly has the ability to work with scp (as well as sftp, rcp, ftp, and lots of others :h netrw-nread) to let you edit files and browse directories that are hosted on a remote machine, inside of your local Vim instance.

This is useful since you are able to use your Vim setup and plugins without copying over your dotfiles to the remote machine. As well, since the file is copied to your local machine, there will be no delay when typing.

Setup

This is optional for Vim, but required for Neovim (check this Neovim issue explaining why).

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

	# https://clang.llvm.org/docs/ClangFormat.html
	# https://clang.llvm.org/docs/ClangFormatStyleOptions.html
	---
	Language: Cpp
	AlignAfterOpenBracket: Align
	AlignConsecutiveAssignments: false # although we like it, it creates churn
	AlignConsecutiveDeclarations: false
	AlignEscapedNewlinesLeft: true
	AlignOperands: true
	AlignTrailingComments: false # churn

	# --------
	# Hardware
	# --------

	# Opcode - operational code
	# Assebly mnemonic - abbreviation for an operation

	# Instruction Code Format (IA-32)
	# - Optional instruction prefix
	# - Operational code