On 12/4/22 18:49, Peter Maydell wrote:
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.
My bad :( Thanks for cleaning up. Reviewed-by: Philippe Mathieu-Daudé <f4...@amsat.org>
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> --- include/hw/block/fdc.h | 3 +-- hw/block/fdc-sysbus.c | 14 +++++++++++--- hw/mips/jazz.c | 2 +- 3 files changed, 13 insertions(+), 6 deletions(-)
