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authorGabriel L. Somlo <somlo@cmu.edu>2015-04-29 11:21:53 -0400
committerGerd Hoffmann <kraxel@redhat.com>2015-06-10 08:06:46 +0200
commit81b2b81062612ebeac4cd5333a3b15c7d79a5a3d (patch)
treec505eeb49687c998e3f536e8e7fe0fbfbf5303b1 /docs/specs
parent0eb973f91521c6bcb6399d25327711d083f6eb10 (diff)
downloadhqemu-81b2b81062612ebeac4cd5333a3b15c7d79a5a3d.zip
hqemu-81b2b81062612ebeac4cd5333a3b15c7d79a5a3d.tar.gz
fw_cfg: insert fw_cfg file blobs via qemu cmdline
Allow user supplied files to be inserted into the fw_cfg device before starting the guest. Since fw_cfg_add_file() already disallows duplicate fw_cfg file names, qemu will exit with an error message if the user supplies multiple blobs with the same fw_cfg file name, or if a blob name collides with a fw_cfg name programmatically added from within the QEMU source code. A warning message will be printed if the fw_cfg item name does not begin with the prefix "opt/", which is recommended for external, user provided blobs. Signed-off-by: Gabriel Somlo <somlo@cmu.edu> Reviewed-by: Laszlo Ersek <lersek@redhat.com> Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Diffstat (limited to 'docs/specs')
-rw-r--r--docs/specs/fw_cfg.txt21
1 files changed, 21 insertions, 0 deletions
diff --git a/docs/specs/fw_cfg.txt b/docs/specs/fw_cfg.txt
index 6accd92..74351dd 100644
--- a/docs/specs/fw_cfg.txt
+++ b/docs/specs/fw_cfg.txt
@@ -203,3 +203,24 @@ completes fully overwriting the item's data.
NOTE: This function is deprecated, and will be completely removed
starting with QEMU v2.4.
+
+== Externally Provided Items ==
+
+As of v2.4, "file" fw_cfg items (i.e., items with selector keys above
+FW_CFG_FILE_FIRST, and with a corresponding entry in the fw_cfg file
+directory structure) may be inserted via the QEMU command line, using
+the following syntax:
+
+ -fw_cfg [name=]<item_name>,file=<path>
+
+where <item_name> is the fw_cfg item name, and <path> is the location
+on the host file system of a file containing the data to be inserted.
+
+NOTE: Users *SHOULD* choose item names beginning with the prefix "opt/"
+when using the "-fw_cfg" command line option, to avoid conflicting with
+item names used internally by QEMU. For instance:
+
+ -fw_cfg name=opt/my_item_name,file=./my_blob.bin
+
+Similarly, QEMU developers *SHOULD NOT* use item names prefixed with
+"opt/" when inserting items programmatically, e.g. via fw_cfg_add_file().
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