Peter Maydell <peter.mayd...@linaro.org> writes: > 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 1430759ec3e we refactored this code > and accidentally lost the setting of dma_chann.
Worth a Fixes: 1430759ec3e4cb92da224d739c914a0e8d78d786 tag? > > 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.) > > Resolves: https://gitlab.com/qemu-project/qemu/-/issues/958 > Signed-off-by: Peter Maydell <peter.mayd...@linaro.org> > Reviewed-by: Philippe Mathieu-Daudé <f4...@amsat.org> > Reviewed-by: Mark Cave-Ayland <mark.cave-ayl...@ilande.co.uk>
