From 2cc06a8843ace3d03464032eb3c74bc6e2b07579 Mon Sep 17 00:00:00 2001 From: Kevin O'Connor Date: Thu, 8 Oct 2015 17:02:58 +0200 Subject: fw_cfg: Define a static signature to be returned on DMA port reads Return a static signature ("QEMU CFG") if the guest does a read to the DMA address io register. Signed-off-by: Kevin O'Connor Reviewed-by: Laszlo Ersek Reviewed-by: Stefan Hajnoczi Signed-off-by: Gerd Hoffmann --- docs/specs/fw_cfg.txt | 3 +++ 1 file changed, 3 insertions(+) (limited to 'docs') diff --git a/docs/specs/fw_cfg.txt b/docs/specs/fw_cfg.txt index 536909a4b2..b8c794f546 100644 --- a/docs/specs/fw_cfg.txt +++ b/docs/specs/fw_cfg.txt @@ -93,6 +93,9 @@ by selecting the "signature" item using key 0x0000 (FW_CFG_SIGNATURE), and reading four bytes from the data register. If the fw_cfg device is present, the four bytes read will contain the characters "QEMU". +If the DMA interface is available, then reading the DMA Address +Register returns 0x51454d5520434647 ("QEMU CFG" in big-endian format). + === Revision / feature bitmap (Key 0x0001, FW_CFG_ID) === A 32-bit little-endian unsigned int, this item is used to check for enabled -- cgit v1.2.3