qemu-options: try and clarify preferred block semantics

Try to correct any confusion about QEMU's Byzantine disk options by
laying out the preferred "modern" options as-per:

 "<danpb> (best:  -device + -blockdev,  2nd obsolete syntax: -device +
     -drive,  3rd obsolete syntax: -drive, 4th obsolete syntax: -hdNN)"

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Acked-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Cc: qemu-block@nongnu.org
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Hanna Reitz <hreitz@redhat.com>
Cc: Thomas Huth <thuth@redhat.com>
Message-Id: <20220822165608.2980552-7-alex.bennee@linaro.org>
This commit is contained in:
Alex Bennée 2022-08-22 17:56:08 +01:00
parent 00269477c2
commit 5af2b0f6ea

View file

@ -1105,6 +1105,19 @@ DEFHEADING()
DEFHEADING(Block device options:)
SRST
The QEMU block device handling options have a long history and
have gone through several iterations as the feature set and complexity
of the block layer have grown. Many online guides to QEMU often
reference older and deprecated options, which can lead to confusion.
The recommended modern way to describe disks is to use a combination of
``-device`` to specify the hardware device and ``-blockdev`` to
describe the backend. The device defines what the guest sees and the
backend describes how QEMU handles the data.
ERST
DEF("fda", HAS_ARG, QEMU_OPTION_fda,
"-fda/-fdb file use 'file' as floppy disk 0/1 image\n", QEMU_ARCH_ALL)
DEF("fdb", HAS_ARG, QEMU_OPTION_fdb, "", QEMU_ARCH_ALL)