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[Qemu-devel] [PATCH v4 5/5] fw_cfg: document ACPI device node informatio


From: Gabriel L. Somlo
Subject: [Qemu-devel] [PATCH v4 5/5] fw_cfg: document ACPI device node information
Date: Sun, 27 Sep 2015 17:29:02 -0400

Signed-off-by: Gabriel Somlo <address@hidden>
---
 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 bc95404..4d85701 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




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