# K1441–K1445 PCI memory BAR size contract

The caller owns a PCI configuration mapping and must save the command register
and every BAR DWORD before probing size. With memory and I/O decoding disabled,
it writes all ones, reads back the sizing mask, restores the BAR DWORDs and
command register, then verifies readback. A BAR with no assigned base may
publish its measured size and type, but it cannot claim a memory range. A
logical BAR range is published only after restoration and assigned-base
decoding succeed. A probe failure leaves no newly owned range and must still
restore the original device configuration.

The pure decoder distinguishes I/O BARs by bit 0 and memory width by bits
2–1. It accepts 32-bit memory type 0 and 64-bit memory type 2; other memory
types are rejected. It removes the low four flag bits from the sizing mask,
combines the high DWORD for a 64-bit BAR, and requires a nonzero power-of-two
size. The size-only decoder accepts an unassigned BAR. For a range claim,
the decoded base must be nonzero and aligned to that size, and
`base + size` must not overflow. I/O space is never published as memory.

Local positive fixtures cover aligned 32-bit and 64-bit memory BARs and
size-only decoding of unassigned BARs. The
negative fixture supplies a non-contiguous size mask and requires an explicit
`MalformedMask` error with unchanged range ownership. K1445 must measure
actual PCI BAR save/probe/restore and mapped-range bounds in an isolated
guest before development guest acceptance is recorded.