The sysbus floppy controllers (devices sysbus-fdc and sun-fdtwo)
don't support DMA. The core floppy controller code expects this to
be indicated by setting FDCtrl::dma_chann to -1. This used to be
done in the device instance_init functions sysbus_fdc_initfn() and
sun4m_fdc_initfn(), but in commit 1430759ec3 we refactored this code
and accidentally lost the setting of dma_chann.
For sysbus-fdc this has no ill effects because we were redundantly
also setting dma_chann in fdctrl_init_sysbus(), but for sun-fdtwo
this means that guests which try to enable DMA on the floppy
controller will cause QEMU to crash because FDCtrl::dma is NULL.
Set dma_chann to -1 in the common instance init, and remove the
redundant code in fdctrl_init_sysbus() that is also setting it.
There is a six-year-old FIXME comment in the jazz board code to the
effect that in theory it should support doing DMA via a custom DMA
controller. If anybody ever chooses to fix that they can do it by
adding support for setting both FDCtrl::dma_chann and FDCtrl::dma.
(A QOM link property 'dma-controller' on the sysbus device which can
be set to an instance of IsaDmaClass is probably the way to go.)
Fixes: 1430759ec3 ("hw/block/fdc: Extract SysBus floppy controllers to fdc-sysbus.c")
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/958
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Message-Id: <20220505101842.2757905-1-peter.maydell@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Change the '-device help' output from:
Storage devices:
name "floppy", bus floppy-bus, desc "virtual floppy drive"
name "isa-fdc", bus ISA
to:
Storage devices:
name "floppy", bus floppy-bus, desc "virtual floppy drive"
name "isa-fdc", bus ISA, desc "virtual floppy controller"
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20210614193220.2007159-7-philmd@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>
Some machines use floppy controllers via the SysBus interface,
and don't need to pull in all the SysBus code.
Extract the SysBus specific code to a new unit: fdc-sysbus.c,
and add a new Kconfig symbol: "FDC_SYSBUS".
Reviewed-by: John Snow <jsnow@redhat.com>
Acked-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Reviewed-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-id: 20210614193220.2007159-6-philmd@redhat.com
Signed-off-by: John Snow <jsnow@redhat.com>
