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Agent skill

Hypervisor Internals

by mohitmishra786 in mohitmishra786/low-level-dev-skills

Hardware virtualization internals skill for Intel VT-x and AMD-V.

MITAuto-check passed

Install Hypervisor Internals

skills CLI
$ npx skills add mohitmishra786/low-level-dev-skills --skill hypervisor-internals -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install mohitmishra786/low-level-dev-skills hypervisor-internals --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/mohitmishra786/low-level-dev-skills.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/virtualization/hypervisor-internals .claude/skills/hypervisor-internals && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
hypervisor-internals
GitHub stars
253
Token cost
~1.4k tokens
SKILL.md length
394 words
Files
1
Skills in repo
138
Repo updated
First seen
Licence
MIT

At a glance

Hardware virtualization internals skill for Intel VT-x and AMD-V.

  • Works in 10 steps: Virtualization types → Intel VT-x overview → VMCS fields (conceptual) → …
  • Studying VMCS/VMCB
  • SKILL.md covers Purpose, When to Use, Workflow and Common Problems, plus 1 more section
  • Instructions only: no scripts, shell commands, URLs or credentials in SKILL.md

What it does

Hypervisor Internals is an agent skill from mohitmishra786/low-level-dev-skills. Hardware virtualization internals skill for Intel VT-x and AMD-V. Use when studying VMCS/VMCB, EPT/NPT page tables, VMEXIT handling, APIC virtualization, or building minimal hypervisors. Activates on queries about VMX, SVM, VMCS, EPT, NPT, VMEXIT, or type-1 hypervisor.

Its SKILL.md is about 1.4k tokens, which your agent loads only when the skill is triggered. It is a single SKILL.md file with no bundled scripts.

The repository describes itself as: A curated suite of AI agent skills for systems and low-level programming with C/C++, Rust, and Zig toolchains, covering compilers, debuggers, profilers, build systems…. The licence is MIT.

When your agent uses it

  • Studying VMCS/VMCB
  • EPT/NPT page tables
  • VMEXIT handling
  • APIC virtualization

Example prompts

  • “/hypervisor-internals”

Workflow steps

10 steps, taken from the step headings in SKILL.md.

  1. Virtualization types
  2. Intel VT-x overview
  3. VMCS fields (conceptual)
  4. AMD SVM (AMD-V)
  5. EPT / NPT — second-level paging
  6. MSR and I/O bitmaps
  7. APIC virtualization
  8. Virtual interrupt injection
  9. Minimal hypervisor references
  10. KVM ioctl interface (practical)

What it can do on your machine

Read from SKILL.md and the folder at commit bdc5847. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    No scripts in the folder and no shell commands in SKILL.md (its code samples are c and bash).

    From the folder's file list and the shell code blocks in SKILL.md.

  • Network

    No URLs in SKILL.md.

    From URLs in SKILL.md, links to its own repository left out.

  • Credentials

    Names no API keys, tokens, secrets or passwords.

    From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Hypervisor Internals loads about 1.4k tokens when it runs. Until then it costs about 73 tokens; SKILL.md has 394 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~73
When it runs · the whole SKILL.md, loaded when a task matches
~1.4k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Auto-check passed

The automated check found no risky patterns in SKILL.md.

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from mohitmishra786/low-level-dev-skills at commit bdc5847, republished under its MIT licence (© mohitmishra786). 394 words, ~1,414 tokens.

Download SKILL.mdSave it as .claude/skills/hypervisor-internals/SKILL.md (or your agent's skills folder).
name
hypervisor-internals
description
Hardware virtualization internals skill for Intel VT-x and AMD-V. Use when studying VMCS/VMCB, EPT/NPT page tables, VMEXIT handling, APIC virtualization, or building minimal hypervisors. Activates on queries about VMX, SVM, VMCS, EPT, NPT, VMEXIT, or type-1 hypervisor.

Hypervisor Internals

Purpose

Explain hardware virtualization internals for agents: Intel VT-x (VMXON, VMCS, VMLAUNCH/VMRESUME, VMEXIT reasons), AMD SVM (VMCB, #VMEXIT), Extended/Nested Page Tables (EPT/NPT), APIC virtualization, MSR bitmaps, virtual interrupt injection, and references for building minimal type-1 hypervisors.

When to Use

  • Understanding how KVM, Hyper-V, or VMware map to hardware features
  • Debugging VMEXIT storms or EPT violations
  • Studying hypervisor security research (CVE triage)
  • Building educational hypervisors (SimpleVisor, hvpp)
  • Tuning nested virtualization performance
  • Analyzing VM escape or side-channel mitigations

Workflow

1. Virtualization types
Type 1 (bare metal)     Type 2 (hosted)
├── Hyper-V             ├── KVM + QEMU
├── Xen                 ├── VirtualBox
├── VMware ESXi         └── Parallels
└── Runs directly on HW     Runs on host OS
2. Intel VT-x overview
VMX operation
├── VMXON — enter VMX root mode
├── VMCS setup — guest/host state fields
├── VMLAUNCH / VMRESUME — enter guest
├── Guest runs until VMEXIT
└── VMXOFF — exit VMX operation

Key structures:

  • VMCS (Virtual Machine Control Structure) — guest/host state, control fields
  • VMEXIT — forced exit to hypervisor (I/O, MSR, EPT fault, interrupt)
c
// Simplified VMX enable check (kernel/driver context)
#include <linux/cpufeature.h>
if (boot_cpu_has(X86_FEATURE_VMX))
    // VT-x supported
3. VMCS fields (conceptual)
CategoryExamples
Guest stateGPRs, CR0/3/4, segment selectors, RIP, RSP
Host stateHost RIP (VMEXIT handler), host CR3
ControlPin-based, proc-based, VMEXIT/entry controls
Exit infoExit reason, qualification, guest-linear-address

VMEXIT reasons (common):

Exit reason codes (Intel)
├── 10 — CPUID
├── 28 — CR access
├── 30 — I/O instruction
├── 48 — EPT violation
├── 0  — External interrupt
└── 1  — Triple fault
4. AMD SVM (AMD-V)
SVM operation
├── EFER.SVME = 1
├── VMCB setup — guest save area + control area
├── VMRUN — enter guest
├── #VMEXIT — exit to host handler
└── Guest state in VMCB

VMCB control area: intercept vectors (CPUID, MSR, IO), nested paging enable, ASID.

IntelAMD
VMCSVMCB
VMXON/VMXOFFEFER.SVME
VMLAUNCH/VMRESUMEVMRUN
EPTNPT (Nested Page Tables)
5. EPT / NPT — second-level paging
Guest virtual (GVA) → Guest physical (GPA) [guest page tables]
GPA → Host physical (HPA) [EPT/NPT, managed by hypervisor]

EPT violation VMEXIT: guest accessed unmapped GPA or violated permissions.

bash
# KVM EPT stats (if available)
# Nested virtualization adds second EPT walk — perf cost

Mitigations for side channels: flush L1D on VMEXIT (MDS), cache partitioning.

6. MSR and I/O bitmaps
MSR bitmap (4KB)
├── Per-MSR read/write intercept control
└── Avoid VMEXIT on common MSRs for performance

I/O bitmap
├── Intercept specific port I/O
└── Pass-through unlisted ports

Hypervisors intercept MSR_IA32_FEATURE_CONTROL, MSR_IA32_EFER, etc.

7. APIC virtualization
APIC virtualization
├── Virtual interrupt delivery — reduce VMEXIT on EOI
├── Posted interrupts — hardware-assisted injection
└── TPR shadowing — avoid exit on priority changes

Reduces overhead for interrupt-heavy guests (network I/O).

8. Virtual interrupt injection

Intel: inject via VM-entry interruption-information field. AMD: V_IRQ, V_INTR_PRIO in VMCB.

Device interrupt → host IRQ handler → hypervisor
    → inject virtual IRQ to guest IDT
    → guest ISR runs
Show full SKILL.md (161 more words)Show less
9. Minimal hypervisor references
ProjectPlatformNotes
SimpleVisorWindowsEducational, few thousand lines
hvppWindowsC++ hypervisor library
kvmmLinuxMinimal KVM study
barevisorx86_64Rust/ASM educational

Study path:

  1. CPUID detection and VMX enable
  2. Allocate VMCS, set host/guest state
  3. Handle VMEXIT for CPUID and HLT
  4. Add EPT with identity map
  5. Inject interrupts
10. KVM ioctl interface (practical)
c
// Userspace KVM (how QEMU talks to KVM)
int kvm = open("/dev/kvm", O_RDWR);
int vm = ioctl(kvm, KVM_CREATE_VM, 0);
int vcpu = ioctl(vm, KVM_CREATE_VCPU, 0);
ioctl(vcpu, KVM_RUN, 0);  // runs until VMEXIT

Common Problems

SymptomCauseFix
VMEXIT storm on MSRMSR bitmap intercepts allFine-tune bitmap; pass-through safe MSRs
EPT misconfigurationMismatched GPA→HPAVerify EPT PTE permissions
Nested virt slowDouble page walkHardware assist; limit nesting depth
VMXON failsCR0/CR4 fixed bitsSet required CR bits per Intel SDM
Guest triple faultBad IDT or unhandled exceptionCheck guest interrupt setup
I/O intercept overheadAll ports trappedShrink I/O bitmap
  • skills/virtualization/qemu-kvm — practical KVM/QEMU usage
  • skills/virtualization/containers-internals — lighter isolation without full VM
  • skills/kernel/kernel-internals — host kernel scheduler/memory
  • skills/kernel/os-dev-scratch — guest OS development context
  • skills/security/kernel-security — hypervisor CVE mitigations
  • skills/platform/riscv-privileged — RISC-V H-extension virtualization

© mohitmishra786, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

Just SKILL.md in skills/virtualization/hypervisor-internals of mohitmishra786/low-level-dev-skills.

Open the folder on GitHubat commit bdc5847

Compare with similar skills

Hypervisor Internals next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Hypervisor Internals compared with similar skills
SkillStarsUsed inTokensAuto-checkLicenceRepo updated
Hypervisor Internals this skillmohitmishra786/low-level-dev-skills253—~1.4kAutomated safety check: PassMIT
Internal Commsalirezarezvani/claude-skills28k—~3.4kAutomated safety check: PassMIT
Internal Communicationsickn33/agentic-awesome-skills47k1 repos~3.4kAutomated safety check: PassMIT
Internal Communications Writeranthropics/skills180k38 repos~378Automated safety check: PassApache-2.0
Internal Comms Anthropicsickn33/agentic-awesome-skills47k1 repos~702Automated safety check: PassApache-2.0
Nofollow Internalthedaviddias/Front-End-Checklist74k—~579Automated safety check: PassMIT

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Questions about Hypervisor Internals

What does Hypervisor Internals do?

Hardware virtualization internals skill for Intel VT-x and AMD-V. Hypervisor Internals is an agent skill from mohitmishra786/low-level-dev-skills. Hardware virtualization internals skill for Intel VT-x and AMD-V.

When should I use Hypervisor Internals?

Hypervisor Internals fits situations like: studying VMCS/VMCB; EPT/NPT page tables; VMEXIT handling; APIC virtualization.

How do I install Hypervisor Internals in Claude Code?

Run `npx skills add mohitmishra786/low-level-dev-skills --skill hypervisor-internals -a claude-code`. Or copy the skill folder (skills/virtualization/hypervisor-internals in mohitmishra786/low-level-dev-skills) into .claude/skills/hypervisor-internals in your project. Claude Code loads it when a task matches its description.

How do I install Hypervisor Internals in Codex?

Run `npx skills add mohitmishra786/low-level-dev-skills --skill hypervisor-internals -a codex`. Or copy the skill folder (skills/virtualization/hypervisor-internals in mohitmishra786/low-level-dev-skills) into .agents/skills/hypervisor-internals in your project. Codex loads it when a task matches its description.

Can I use Hypervisor Internals in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add mohitmishra786/low-level-dev-skills --skill hypervisor-internals -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/hypervisor-internals, .gemini/skills/hypervisor-internals, .github/skills/hypervisor-internals and .opencode/skills/hypervisor-internals in your project.

What does Hypervisor Internals need to run?

SKILL.md names no scripts, command-line tools or credentials: Hypervisor Internals is instructions for the agent only.

Does Hypervisor Internals access the network?

SKILL.md contains no URLs. Any network use would come from the scripts or tools the agent runs. This is read from the text; nothing was executed.

Is Hypervisor Internals safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Hypervisor Internals use?

Hypervisor Internals is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Hypervisor Internals use?

About 1.4k tokens (SKILL.md is roughly 5.7k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Hypervisor Internals?

Skills that share tags, products or a category with Hypervisor Internals: Internal Comms (alirezarezvani/claude-skills, 28k stars), Internal Communication (sickn33/agentic-awesome-skills, 47k stars), Internal Communications Writer (anthropics/skills, 180k stars) and Internal Comms Anthropic (sickn33/agentic-awesome-skills, 47k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Hypervisor Internals?

mohitmishra786 (a GitHub user) maintains it in mohitmishra786/low-level-dev-skills, which has 253 GitHub stars. The repository holds 138 skills in this directory. The repository was last updated on June 27, 2026.

Source: mohitmishra786/low-level-dev-skills on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.