Re: [Qemu-devel] [PATCH 0/4] block: Improve warnings for doubly-connected drives

[Peter Maydell <peter.maydell@linaro.org>]

Ping?

thanks
-- PMM

On 12 June 2015 at 14:26, Peter Maydell <peter.maydell@linaro.org> wrote:
> 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.
>
> The patchset improves some error messages, and makes some previously
> undiagnosed mistakes into warnings. The changes (with sample x86
> command lines to provoke them) are:
>
> (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: an error:
>   qemu-system-x86_64: -device ide-hd,drive=foo: Property 'ide-hd.drive'
>   can't take value 'foo', it's in use
>
> Now: a better error:
>   qemu-system-x86_64: -device ide-hd,drive=foo: Property 'ide-hd.drive'
>   can't be set to drive ID 'foo'; that drive has been automatically
>   connected to another device. Use if=none if you do not want that
>   automatic connection.
>
> (2) As 1, but the board does not handle this if= type:
>
> Previously: not diagnosed at all
>
> Now: a warning:
>   Warning: automatic connection of this drive requested (because if=sd
>   was specified) but it was also connected manually to a device:
>   id=foo,file=tmp.qcow2,if=sd,bus=0,unit=0
>   (If you don't want this drive auto-connected, use if=none.)
>
> [This means we now will always warn one way or another about drives which
> have an if= auto-connect specified but which the board didn't pick up: either
> they're also manually connected and get this warning, or they're not manually
> connected, and get the orphan-drive warning. If the if= was due to the
> board default rather than the user typing it specifically, the error message
> text is slightly different to reflect that.]
>
> (3) Drive specified to be manually connected in two different ways:
>
>   qemu-system-x86_64 -nodefaults -display none -drive if=sd,file=tmp.qcow2,id=foo -device ide-hd,drive=foo -device ide-hd,drive=foo
>
> Previously: an error:
>   qemu-system-x86_64: -device ide-hd,drive=foo: Property 'ide-hd.drive'
>   can't take value 'foo', it's in use
>
> Now: a better error:
>   qemu-system-x86_64: -device ide-hd,drive=foo: Property 'ide-hd.drive'
>   can't be set to drive ID 'foo'; that drive has already been connected
>   to another device.
>
>
>
> In order to detect when a drive was auto-connected, we need to set a
> flag in the DriveInfo when this happens.  we do this by assuming that
> all calls to blk_by_legacy_dinfo() imply that we're about to assign
> the drive to a device.  This is a slightly ugly place to make the
> test, but simpler than trying to locate and change every place in the
> code that does automatic drive handling, and the worst case is that
> we might print out a spurious warning.
>
>
> I include patch #4 as the motivation/context but in fact it doesn't
> depend on the first 3, so if you want to take the first 3 via
> block and have me put the 4th one in target-arm that's OK.
>
> thanks
> -- PMM
>
>
> Peter Maydell (4):
>   block: Warn if an if=<something> drive was also connected manually
>   qdev-properties-system: Change set_pointer's parse callback to use
>     Error
>   qdev-properties-system: Improve error message for drive assignment
>     conflict
>   hw/arm/virt: Make block devices default to virtio
>
>  block/block-backend.c            |  4 ++++
>  blockdev.c                       | 39 ++++++++++++++++++++++++++++++++++
>  hw/arm/virt.c                    |  2 ++
>  hw/core/qdev-properties-system.c | 45 ++++++++++++++++++++++++++++------------
>  include/sysemu/blockdev.h        |  2 ++
>  5 files changed, 79 insertions(+), 13 deletions(-)