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fw_cfg: Define a static signature to be returned on DMA port reads

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Return a static signature ("QEMU CFG") if the guest does a read to the
DMA address io register.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Kevin O'Connor 2015-10-08 17:02:58 +02:00 • committed by Gerd Hoffmann
parent c886fc4c20
commit 2cc06a8843
2 changed files with 15 additions and 2 deletions
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3
docs/specs/fw_cfg.txt
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@ -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