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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>
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@ -864,7 +864,8 @@ ETEXI
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DEF("blockdev", HAS_ARG, QEMU_OPTION_blockdev,
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"-blockdev [driver=]driver[,node-name=N][,discard=ignore|unmap]\n"
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" [,cache.direct=on|off][,cache.no-flush=on|off]\n"
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" [,read-only=on|off][,detect-zeroes=on|off|unmap]\n"
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" [,read-only=on|off][,auto-read-only=on|off]\n"
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" [,force-share=on|off][,detect-zeroes=on|off|unmap]\n"
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" [,driver specific parameters...]\n"
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" configure a block backend\n", QEMU_ARCH_ALL)
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STEXI
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@ -900,6 +901,25 @@ name is not intended to be predictable and changes between QEMU invocations.
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For the top level, an explicit node name must be specified.
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@item read-only
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Open the node read-only. Guest write attempts will fail.
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Note that some block drivers support only read-only access, either generally or
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in certain configurations. In this case, the default value
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@option{read-only=off} does not work and the option must be specified
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explicitly.
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@item auto-read-only
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If @option{auto-read-only=on} is set, QEMU may fall back to read-only usage
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even when @option{read-only=off} is requested, or even switch between modes as
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needed, e.g. depending on whether the image file is writable or whether a
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writing user is attached to the node.
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@item force-share
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Override the image locking system of QEMU by forcing the node to utilize
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weaker shared access for permissions where it would normally request exclusive
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access. When there is the potential for multiple instances to have the same
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file open (whether this invocation of QEMU is the first or the second
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instance), both instances must permit shared access for the second instance to
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succeed at opening the file.
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Enabling @option{force-share=on} requires @option{read-only=on}.
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@item cache.direct
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The host page cache can be avoided with @option{cache.direct=on}. This will
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attempt to do disk IO directly to the guest's memory. QEMU may still perform an
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