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.
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.maydell@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(-)
diff --git a/include/hw/block/fdc.h b/include/hw/block/fdc.h
index 1ecca7cac7f..35248c08379 100644
--- a/include/hw/block/fdc.h
+++ b/include/hw/block/fdc.h
@@ -10,8 +10,7 @@
#define TYPE_ISA_FDC "isa-fdc"
void isa_fdc_init_drives(ISADevice *fdc, DriveInfo **fds);
-void fdctrl_init_sysbus(qemu_irq irq, int dma_chann,
- hwaddr mmio_base, DriveInfo **fds);
+void fdctrl_init_sysbus(qemu_irq irq, hwaddr mmio_base, DriveInfo **fds);
void sun4m_fdctrl_init(qemu_irq irq, hwaddr io_base,
DriveInfo **fds, qemu_irq *fdc_tc);
diff --git a/hw/block/fdc-sysbus.c b/hw/block/fdc-sysbus.c
index 57fc8773f12..6c22c3510da 100644
--- a/hw/block/fdc-sysbus.c
+++ b/hw/block/fdc-sysbus.c
@@ -94,8 +94,7 @@ static void fdctrl_handle_tc(void *opaque, int irq, int level)
trace_fdctrl_tc_pulse(level);
}
-void fdctrl_init_sysbus(qemu_irq irq, int dma_chann,
- hwaddr mmio_base, DriveInfo **fds)
+void fdctrl_init_sysbus(qemu_irq irq, hwaddr mmio_base, DriveInfo **fds)
{
FDCtrl *fdctrl;
DeviceState *dev;
@@ -105,7 +104,6 @@ void fdctrl_init_sysbus(qemu_irq irq, int dma_chann,
dev = qdev_new("sysbus-fdc");
sys = SYSBUS_FDC(dev);
fdctrl = &sys->state;
- fdctrl->dma_chann = dma_chann; /* FIXME */
sbd = SYS_BUS_DEVICE(dev);
sysbus_realize_and_unref(sbd, &error_fatal);
sysbus_connect_irq(sbd, 0, irq);
@@ -138,6 +136,16 @@ static void sysbus_fdc_common_instance_init(Object *obj)
FDCtrlSysBus *sys = SYSBUS_FDC(obj);
FDCtrl *fdctrl = &sys->state;
+ /*
+ * DMA is not currently supported for sysbus floppy controllers.
+ * If we wanted to add support then probably the best approach is
+ * to have a QOM link property 'dma-controller' which the board
+ * code can set to an instance of IsaDmaClass, and an integer
+ * property 'dma-channel', so that we can set fdctrl->dma and
+ * fdctrl->dma_chann accordingly.
+ */
+ fdctrl->dma_chann = -1;
+
qdev_set_legacy_instance_id(dev, 0 /* io */, 2); /* FIXME */
memory_region_init_io(&fdctrl->iomem, obj,
diff --git a/hw/mips/jazz.c b/hw/mips/jazz.c
index 44f0d48bfd7..14eaa517435 100644
--- a/hw/mips/jazz.c
+++ b/hw/mips/jazz.c
@@ -354,7 +354,7 @@ static void mips_jazz_init(MachineState *machine,
fds[n] = drive_get(IF_FLOPPY, 0, n);
}
/* FIXME: we should enable DMA with a custom IsaDma device */
- fdctrl_init_sysbus(qdev_get_gpio_in(rc4030, 1), -1, 0x80003000, fds);
+ fdctrl_init_sysbus(qdev_get_gpio_in(rc4030, 1), 0x80003000, fds);
/* Real time clock */
mc146818_rtc_init(isa_bus, 1980, NULL);