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[PULL 5/7] doc: Describe missing generic -blockdev options
From: |
Kevin Wolf |
Subject: |
[PULL 5/7] doc: Describe missing generic -blockdev options |
Date: |
Fri, 25 Oct 2019 15:46:09 +0200 |
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 <address@hidden>
Reviewed-by: Peter Maydell <address@hidden>
---
qemu-options.hx | 22 +++++++++++++++++++++-
1 file changed, 21 insertions(+), 1 deletion(-)
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
--
2.20.1
- [PULL 0/7] Block layer patches, Kevin Wolf, 2019/10/25
- [PULL 2/7] iotests: Skip read-only cases in 118 when run as root, Kevin Wolf, 2019/10/25
- [PULL 4/7] block/backup: drop dead code from backup_job_create, Kevin Wolf, 2019/10/25
- [PULL 1/7] qapi: add support for blkreplay driver, Kevin Wolf, 2019/10/25
- [PULL 5/7] doc: Describe missing generic -blockdev options,
Kevin Wolf <=
- [PULL 3/7] blockdev: Use error_report() in hmp_commit(), Kevin Wolf, 2019/10/25
- [PULL 7/7] qcow2: Fix corruption bug in qcow2_detect_metadata_preallocation(), Kevin Wolf, 2019/10/25
- [PULL 6/7] coroutine: Add qemu_co_mutex_assert_locked(), Kevin Wolf, 2019/10/25
- Re: [PULL 0/7] Block layer patches, Peter Maydell, 2019/10/25