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...) Changes v1->v2: * drop "warn if an if=<something> drive was also connected manually" patch * change implementation of "improve error message" patch Peter Maydell (3): 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 hw/arm/virt.c | 2 ++ hw/core/qdev-properties-system.c | 42 +++++++++++++++++++++++++++------------- 2 files changed, 31 insertions(+), 13 deletions(-) -- 1.9.1