Re: [Qemu-block] [Qemu-devel] [PATCH v2 for-2.4 0/3] block: Improve warnings for doubly-connected drives

[Markus Armbruster]

Peter Maydell <address@hidden> writes:

> This patchset attempts to improve the warning and error messages for
> bad user command lines that attempt to connect a drive up to two
> devices. The motivation here is patch #4, which changes the default
> interface for the virt board to virtio. That will break some existing
> command lines which forgot to specify if=none, and so I would like
> us to at least diagnose that user error in a helpful way that points
> the user towards adding the missing if=none.
>
> Version 2 reduces scope, because it turns out that it is harder than
> we thought to identify whether a use of an if=something drive is the
> auto-plugging or a manual wiring up to a device. So all we do here
> is improve the error messages for two situations which were already
> errors but with rather cryptic messages:
>
>     (1) Drive specified as to be auto-connected and also manually connected
>     (and the board does handle this if= type):
>     
>       qemu-system-x86_64 -nodefaults -display none \
>          -drive if=scsi,file=tmp.qcow2,id=foo -device ide-hd,drive=foo
>     
>     Previously:
>       qemu-system-x86_64: -device ide-hd,drive=foo: Property 'ide-hd.drive'
>       can't take value 'foo', it's in use
>     
>     Now:
>       qemu-system-x86_64: -device ide-hd,drive=foo: Drive 'foo' is already in
>       use because it has been automatically connected to another device (did
>       you need 'if=none' in the drive options?)
>     
>     (2) Drive specified to be manually connected in two different ways:
>     
>       qemu-system-x86_64 -nodefaults -display none \
>        -drive if=none,file=tmp.qcow2,id=foo -device ide-hd,drive=foo \
>        -device ide-hd,drive=foo
>     
>     Previously:
>       qemu-system-x86_64: -device ide-hd,drive=foo: Property 'ide-hd.drive'
>       can't take value 'foo', it's in use
>     
>     Now:
>       qemu-system-x86_64: -device ide-hd,drive=foo: Drive 'foo' is already in
>       use by another device
>
> (We'll also produce message 1 in the oddball case where the user creates
> a drive if=something-not-handled-by-machine and then wires it up manually
> to two different devices; in this case their command line is doubly broken
> and if they use if=none as suggested by message 1 they'll then get message 2
> and can fix their own double-usage...)

With the commit message of PATCH 3 amended, series
Reviewed-by: Markus Armbruster <address@hidden>