Commit c9b749d7 authored by Kevin Wolf's avatar Kevin Wolf
Browse files

doc: Describe missing generic -blockdev options 



We added more generic options after introducing -blockdev and forgot to
update the documentation (man page and --help output) accordingly. Do
that now.

Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
Reviewed-by: default avatarPeter Maydell <peter.maydell@linaro.org>
parent 8ccf458a

qemu-options.hx

+21 −1
Original line number Diff line number Diff line
@@ -864,7 +864,8 @@ ETEXI 
DEF("blockdev", HAS_ARG, QEMU_OPTION_blockdev,

    "-blockdev [driver=]driver[,node-name=N][,discard=ignore|unmap]\n"

    "          [,cache.direct=on|off][,cache.no-flush=on|off]\n"

    "          [,read-only=on|off][,detect-zeroes=on|off|unmap]\n"

    "          [,read-only=on|off][,auto-read-only=on|off]\n"

    "          [,force-share=on|off][,detect-zeroes=on|off|unmap]\n"

    "          [,driver specific parameters...]\n"

    "                configure a block backend\n", QEMU_ARCH_ALL)

STEXI
@@ -900,6 +901,25 @@ name is not intended to be predictable and changes between QEMU invocations. 
For the top level, an explicit node name must be specified.

@item read-only

Open the node read-only. Guest write attempts will fail.



Note that some block drivers support only read-only access, either generally or

in certain configurations. In this case, the default value

@option{read-only=off} does not work and the option must be specified

explicitly.

@item auto-read-only

If @option{auto-read-only=on} is set, QEMU may fall back to read-only usage

even when @option{read-only=off} is requested, or even switch between modes as

needed, e.g. depending on whether the image file is writable or whether a

writing user is attached to the node.

@item force-share

Override the image locking system of QEMU by forcing the node to utilize

weaker shared access for permissions where it would normally request exclusive

access.  When there is the potential for multiple instances to have the same

file open (whether this invocation of QEMU is the first or the second

instance), both instances must permit shared access for the second instance to

succeed at opening the file.



Enabling @option{force-share=on} requires @option{read-only=on}.

@item cache.direct

The host page cache can be avoided with @option{cache.direct=on}. This will

attempt to do disk IO directly to the guest's memory. QEMU may still perform an