[PATCH v2 1/3] fdc: Drop deprecated floppy configuration

[Markus Armbruster]

Peter Krempa <pkrempa at redhat.com> writes:

> On Thu, Mar 04, 2021 at 17:23:05 +0100, Markus Armbruster wrote:
>> Daniel P. Berrangé <berrange at redhat.com> writes:
>> 
>> > On Thu, Mar 04, 2021 at 03:26:55PM +0100, Markus Armbruster wrote:
>> >> Daniel P. Berrangé <berrange at redhat.com> writes:
>> >> 
>> >> > On Thu, Mar 04, 2021 at 11:00:57AM +0100, Markus Armbruster wrote:
>> >> >> Drop the crap deprecated in commit 4a27a638e7 "fdc: Deprecate
>> >> >> configuring floppies with -global isa-fdc" (v5.1.0).
>> >> >> 
>> >> >> Signed-off-by: Markus Armbruster <armbru at redhat.com>
>> >> >> ---
>> >> >>  docs/system/deprecated.rst       |  26 --
>> >> >>  docs/system/removed-features.rst |  26 ++
>> >> >>  hw/block/fdc.c                   |  54 +--
>> >> >>  tests/qemu-iotests/172           |  31 +-
>> >> >>  tests/qemu-iotests/172.out       | 562 +------------------------------
>> >> >>  5 files changed, 30 insertions(+), 669 deletions(-)
>
> [...]
>
>> >> 
>> >> Correct.
>> >> 
>> >> This was deprecated in commit 4a27a638e7 "fdc: Deprecate configuring
>> >> floppies with -global isa-fdc" (v5.1.0).  Since then, its use triggers a
>> >> warning:
>> >> 
>> >>     $ qemu-system-x86_64 -nodefaults -M q35 -display none -drive if=none,id=drive-fdc0-0-0 -device isa-fdc,driveA=drive-fdc0-0-0,bootindexA=1
>> >>     qemu-system-x86_64: -device isa-fdc,driveA=drive-fdc0-0-0,bootindexA=1: warning: warning: property isa-fdc.driveA is deprecated
>> >>     Use -device floppy,unit=0,drive=... instead.
>> >> 
>> >> Note the -M q35.  Needed because the default machine type has an onboard
>> >> isa-fdc, which cannot be configured this way.
>> >> 
>> >> Sadly, the commit's update of docs/system/deprecated.rst neglects to
>> >> cover this use.  Looks the series overtaxed my capacity to juggle
>> >> details; my apologies.
>> >> 
>> >> Is libvirt still using these properties?
>> >
>> > Unfortunately yes, but it seems like it ought to be fairly easy to
>> > change the syntax. Just need to figure out what the right way to
>> > detect the availability of the new syntax is. Presumably just look
>> > for existance of the 'floppy' device type ?
>> 
>> Yes.  The device type was added in merge commit fd209e4a7, v2.8.0.
>> 
>> > Can you confirm that switching from -global to the new -device floppy
>> > does /not/ have any live migration impact ?
>> 
>> Yes, it must not affect migration.
>> 
>> When Kevin split the floppy device type off the floppy controller, he
>> had to add some moderately ugly hackery to keep the old qdev properties
>> working.  Think propagate property values to floppy from controller,
>> which otherwise ignores them.
>> 
>> The way you get the values into the floppy device cannot affect the
>> migration data.  Only different values can.
>> 
>> This patch removes a deprecated way.
>
> Note that when QEMU_CAPS_BLOCKDEV is asserted we format floppies as:
>
> -blockdev '{"driver":"file","filename":"/tmp/firmware.img",\
> "node-name":"libvirt-2-storage","auto-read-only":true,"discard":"unmap"}' \
> -blockdev '{"node-name":"libvirt-2-format","read-only":false,"driver":"raw",\
> "file":"libvirt-2-storage"}' \
> -device floppy,unit=0,drive=libvirt-2-format,id=fdc0-0-0 \
> -blockdev '{"driver":"file","filename":"/tmp/data.img",\
> "node-name":"libvirt-1-storage","auto-read-only":true,"discard":"unmap"}' \
> -blockdev '{"node-name":"libvirt-1-format","read-only":false,"driver":"qcow2",\
> "file":"libvirt-1-storage"}' \
> -device floppy,unit=1,drive=libvirt-1-format,id=fdc0-0-1 \
>
> as visible in the test file:
>
> tests/qemuxml2argvdata/disk-floppy-q35-2_11.x86_64-latest.args
>
> So libvirt should be in the clear. isa-fdc with driveA/driveB is
> formatted only when the blockdev capability isn't present.

Even better: in the clear for some time already, which means a wider
range of libvirt versions keeps working with the latest QEMU.  Nice,
because keeping the coupling reasonably lose makes upgrading easier.

Thanks!