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fw_cfg: document ACPI device node information

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Signed-off-by: Gabriel Somlo <somlo@cmu.edu>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Marc Marí <markmb@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Message-id: 1455906029-25565-6-git-send-email-somlo@cmu.edu
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Gabriel L. Somlo 2016-02-19 13:20:29 -05:00 committed by Gerd Hoffmann
parent 70bee80d6b
commit 36a43ea83b
1 changed files with 9 additions and 0 deletions
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docs/specs/fw_cfg.txt
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@ -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) ===