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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: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
This commit is contained in:
Kevin Wolf 2019-10-15 12:29:58 +02:00
parent 8ccf458af5
commit c9b749d7bc
1 changed files with 21 additions and 1 deletions
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22
qemu-options.hx
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@ -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