cpu.toml

# Standard CPU definition for the deterministic VMM.
#
# Defines the exact CPUID responses for our virtual CPU. The VMM loads this at startup and uses
# it as a lookup table: for any (leaf, subleaf) the guest queries, return the values here. For
# leaves not listed, return all zeros.
#
# Design goals:
# - Enough features for 64-bit Linux to boot and run userspace
# - No features that imply hardware we don't emulate (XSAVE/AVX, VMX, RDRAND)
# - Fixed identity across all host CPUs for cross-machine determinism
# - Intel vendor string so the kernel uses leaf 0x15 for TSC frequency
#
# Based loosely on Skylake (family 6, model 0x5E) but this is a fictional CPU — the model
# number is just a hint to the kernel about what generation of quirks to apply.

# ============================================================================
# Leaf 0x00 — Basic CPUID: max standard leaf + vendor string
# ============================================================================
[[cpuid]]
leaf = 0x00000000
subleaf = 0x00000000
eax = 0x00000016  # max standard leaf
ebx = 0x756E6547  # "Genu"
ecx = 0x6C65746E  # "ntel"
edx = 0x49656E69  # "ineI"

# ============================================================================
# Leaf 0x01 — Version info + feature flags
# ============================================================================
[[cpuid]]
leaf = 0x00000001
subleaf = 0x00000000
# EAX encodes family/model/stepping:
#   stepping      = 3       (bits 3:0)
#   model low     = 0xE     (bits 7:4)
#   family        = 6       (bits 11:8)
#   model high    = 0x5     (bits 19:16)
#   → family 6, model 0x5E (94 = Skylake-S), stepping 3
eax = 0x000506E3
# EBX: brand=0, CLFLUSH line=64 bytes (8×8), 1 logical CPU, APIC ID 0
ebx = 0x00010800
# ECX feature flags:
#   bit  0  SSE3            bit 20  SSE4.2
#   bit  9  SSSE3           bit 22  MOVBE
#   bit 13  CMPXCHG16B      bit 23  POPCNT
#   bit 19  SSE4.1
#
# NOT advertised (and why):
#   TSC-Deadline (bit 24) — VMM and KVM patch support it, but the clockevent
#                           min_delta calibration storm at 128 GHz virtual TSC makes
#                           it 24x slower than the legacy periodic timer. See commit
#                           history for details.
#   XSAVE (bit 26)   — we don't emulate XSAVE state areas; guest uses FXSAVE
#   AVX (bit 28)     — requires XSAVE
#   RDRAND (bit 30)  — not advertised until VMCS-level interception works
#   AES-NI (bit 25)  — not needed for boot; can add later
#
# Advertised but not a real CPU feature:
#   HYPERVISOR (bit 31) — tells the kernel it's in a VM. This skips the
#                         microcode version check (which would taint the kernel)
#                         and doesn't commit us to paravirt: leaf 0x40000000
#                         returns zeros, so no kvmclock or PV features activate.
ecx = 0x80D82201
# EDX feature flags:
#   bit  0  FPU       bit 13  PGE        bit 24  FXSR
#   bit  2  DE        bit 14  MCA        bit 25  SSE
#   bit  3  PSE       bit 15  CMOV       bit 26  SSE2
#   bit  4  TSC       bit 16  PAT
#   bit  5  MSR       bit 17  PSE-36
#   bit  6  PAE       bit 19  CLFLUSH
#   bit  7  MCE
#   bit  8  CX8
#   bit  9  APIC
#   bit 11  SEP
#
# NOT advertised:
#   MTRR (bit 12) — no MMIO regions; single flat RAM; just wasted boot-time work
edx = 0x078BEBFD

# ============================================================================
# Leaf 0x06 — Thermal and Power Management
# ============================================================================
[[cpuid]]
leaf = 0x00000006
subleaf = 0x00000000
# EAX bit 2 = ARAT (Always Running APIC Timer): the kernel trusts the APIC timer
# to tick at a constant rate. Essential for our deterministic timer.
eax = 0x00000004
ebx = 0x00000000
ecx = 0x00000000
edx = 0x00000000

# ============================================================================
# Leaf 0x07 — Structured Extended Feature Flags
# ============================================================================
[[cpuid]]
leaf = 0x00000007
subleaf = 0x00000000
eax = 0x00000000  # max subleaf = 0
# EBX:
#   bit  3  BMI1
#   bit  7  SMEP  (Supervisor Mode Execution Prevention)
#   bit  8  BMI2
#   bit  9  ERMS  (Enhanced REP MOVSB/STOSB)
#   bit 20  SMAP  (Supervisor Mode Access Prevention)
ebx = 0x00100388
ecx = 0x00000000
# EDX:
#   bit 29  ARCH_CAPABILITIES — IA32_ARCH_CAPABILITIES MSR is available
edx = 0x20000000

# ============================================================================
# Leaf 0x0B — Extended Topology Enumeration (1 thread, 1 core)
# ============================================================================
[[cpuid]]
leaf = 0x0000000B
subleaf = 0x00000000
eax = 0x00000000  # bits to shift for next-level APIC ID
ebx = 0x00000001  # 1 logical processor at this level
ecx = 0x00000100  # level type 1 = SMT, subleaf 0
edx = 0x00000000  # x2APIC ID

[[cpuid]]
leaf = 0x0000000B
subleaf = 0x00000001
eax = 0x00000000
ebx = 0x00000001  # 1 logical processor
ecx = 0x00000201  # level type 2 = core, subleaf 1
edx = 0x00000000

# Leaves 0x15 (TSC/Crystal Clock) and 0x16 (Processor Frequency) are synthesized by
# the VMM at runtime — they're tightly coupled to the LAPIC timer implementation.
# See CRYSTAL_HZ and TSC_TO_CRYSTAL_RATIO in main.rs.

# ============================================================================
# Leaf 0x40000000 — Hypervisor identification (disabled)
# ============================================================================
# Return zeros so the guest doesn't try KVM paravirt features (kvmclock, etc).
[[cpuid]]
leaf = 0x40000000
subleaf = 0x00000000
eax = 0x00000000
ebx = 0x00000000
ecx = 0x00000000
edx = 0x00000000

# ============================================================================
# Leaf 0x80000000 — Max Extended Leaf
# ============================================================================
[[cpuid]]
leaf = 0x80000000
subleaf = 0x00000000
eax = 0x80000008  # max extended leaf
ebx = 0x00000000
ecx = 0x00000000
edx = 0x00000000

# ============================================================================
# Leaf 0x80000001 — Extended Feature Flags
# ============================================================================
[[cpuid]]
leaf = 0x80000001
subleaf = 0x00000000
eax = 0x00000000
ebx = 0x00000000
# ECX: bit 0 = LAHF/SAHF in 64-bit mode
ecx = 0x00000001
# EDX:
#   bit 11  SYSCALL/SYSRET
#   bit 20  NX (Execute Disable)
#   bit 26  1 GiB pages
#   bit 29  Long Mode (Intel 64)
edx = 0x24100800

# ============================================================================
# Leaves 0x80000002–0x80000004 — Processor Name String
# ============================================================================
# "Deterministic Virtual CPU v1" (28 chars, null-padded to 48 bytes)
# Each leaf returns 16 bytes as EAX[3:0] EBX[7:4] ECX[11:8] EDX[15:12], little-endian.
[[cpuid]]
leaf = 0x80000002
subleaf = 0x00000000
eax = 0x65746544  # "Dete"
ebx = 0x6E696D72  # "rmin"
ecx = 0x69747369  # "isti"
edx = 0x69562063  # "c Vi"

[[cpuid]]
leaf = 0x80000003
subleaf = 0x00000000
eax = 0x61757472  # "rtua"
ebx = 0x5043206C  # "l CP"
ecx = 0x31762055  # "U v1"
edx = 0x00000000

[[cpuid]]
leaf = 0x80000004
subleaf = 0x00000000
eax = 0x00000000
ebx = 0x00000000
ecx = 0x00000000
edx = 0x00000000

# ============================================================================
# Leaf 0x80000008 — Virtual/Physical Address Sizes
# ============================================================================
[[cpuid]]
leaf = 0x80000008
subleaf = 0x00000000
# EAX: physical address bits = 39 (512 GiB), virtual address bits = 48
eax = 0x00003027
ebx = 0x00000000
ecx = 0x00000000
edx = 0x00000000