Signed-off-by: Gabriel Somlo <so...@cmu.edu> --- docs/specs/fw_cfg.txt | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/docs/specs/fw_cfg.txt b/docs/specs/fw_cfg.txt index 5bc7b96..b5f4b5d 100644 --- a/docs/specs/fw_cfg.txt +++ b/docs/specs/fw_cfg.txt @@ -77,6 +77,15 @@ increasing address order, similar to memcpy(). Selector Register IOport: 0x510 Data Register IOport: 0x511 +== ACPI Interface == + +The fw_cfg device is defined with ACPI ID "QEMU0002". Since we expect +ACPI tables to be passed into the guest through the fw_cfg device itself, +the guest-side BIOS can not use ACPI to find fw_cfg. However, once the +bios is finished setting up ACPI tables and hands control over to the +guest kernel, the latter can use the fw_cfg ACPI node for a more accurate +inventory of in-use IOport or MMIO regions. + == Firmware Configuration Items == === Signature (Key 0x0000, FW_CFG_SIGNATURE) === -- 2.4.3
