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Diffstat (limited to 'docs/specs/fw_cfg.txt')
| -rw-r--r-- | docs/specs/fw_cfg.txt | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/docs/specs/fw_cfg.txt b/docs/specs/fw_cfg.txt index 2099ad9a4d..5414140f33 100644 --- a/docs/specs/fw_cfg.txt +++ b/docs/specs/fw_cfg.txt @@ -84,6 +84,15 @@ Selector Register address: Base + 8 (2 bytes) Data Register address: Base + 0 (8 bytes) DMA Address address: Base + 16 (8 bytes) +== 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 firmware can not use ACPI to find fw_cfg. However, once the +firmware 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) === |