The native Xbox import __imp__NtAllocateVirtualMemory at 0x82ACB99C uses five arguments: guest base-address pointer (r3), guest region-size pointer (r4), allocation flags (r5), protection flags (r6), debug-memory flag (r7). NTSTATUS returns zero-extended in r3. Base and size are 32-bit big-endian in/out words; other argument registers remain unchanged.
The first observed call from sub_824E1018, with LR 0x824E1364, requests base zero, size 0x100000, type 0x60002000, protection 4, debug 0. This reserves a 1 MiB range using 64 KiB pages and the heap flag. The diagnostic records the actual request in out/vm-before.log before enabling the implementation.
The implemented service returns base 0x40000000 and size 0x100000. The game then requests commitment of 0x10000 bytes at that base with flags 0x60001000. This also succeeds, after which guest heap initialization writes its metadata into the committed range and reaches KeGetCurrentProcessType at 0x82ACB59C (LR 0x824E14B8). That was the stop at commit 48b25ea; the subsequent process/initializer increment advances to XboxHardwareInfo. This is progress within initialization, not a playable game.
GuestMemory reserves a 4 GiB host address space once. Guest reservations and host-accessible committed ranges are tracked separately. Reserving a guest range prevents conflicting allocations but does not allow reads or writes. Committing a reserved subrange makes only those logical bytes accessible. New committed storage is zero-initialized by the host; committing it again preserves its contents. Bounds checks cover adjacent committed spans and continue to reject import variables and unmapped gaps.
The virtual allocation service uses bounded diagnostic arenas: 4 KiB pages in [0x10000000, 0x20000000) and 64 KiB pages in [0x40000000, 0x50000000). These are diagnostic allocation choices, not a claim to reproduce Xbox physical memory layout or available hardware memory. Fixed image, PCR, stack and module mappings remain separate. Existing reservations are checked before a new range is claimed. A 4096-reservation metadata budget produces an explicit diagnostic stop; sorted gaps avoid repeatedly scanning every owned page.
- Reserve, commit, or both; a zero-base commit chooses a fresh reserved/committed range.
- Page-aligned fixed base within an owned reservation for commitment; fixed base selects its arena's page size.
- Size rounded upwards to the selected page size using checked arithmetic.
- Read/write protection, heap, nozero and top-down allocation flags. Nozero permits initially zeroed storage; it does not erase existing committed contents.
- Guest output words updated only on success. Null/zero-size and invalid arena requests return
STATUS_INVALID_PARAMETER; arena exhaustion and reservation conflicts returnSTATUS_NO_MEMORY.
Unsupported debug, protection, reset, 16 MiB page and unaligned fixed-base modes stop with a diagnostic instead of being accepted silently. High-bit sizes are not interpreted as negative allocation requests. Release, decommit, query and protection imports remain separate, unimplemented services. This is a single-threaded diagnostic service with bounded metadata; it is not a completed kernel memory subsystem. The verified Windows host uses 4 KiB host pages; hosts with larger pages may stop on small-page requests and have not been validated.
Runtime ABI, flag values and existing-reservation behavior were checked against Xenia memory imports and Xbox constants at the already recorded reference revision. The diagnostic deliberately supports a narrower request set and stops on the remaining modes.