diff options
| -rw-r--r-- | qemu-options.hx | 22 |
1 files changed, 21 insertions, 1 deletions
diff --git a/qemu-options.hx b/qemu-options.hx index 996b6fba74..19709f973d 100644 --- a/qemu-options.hx +++ b/qemu-options.hx @@ -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 |