Re: [Qemu-devel] [PATCH v2 2/6] qdev: reset qdev along with qdev tree

[Stefan Weil]

Am 19.11.2010 10:55, schrieb Isaku Yamahata:
> From: Anthony Liguori <address@hidden>
>
> This patch changes the reset handling so that qdev has no knowledge of the
> global system reset. Instead, a new bus/device level function is 
> introduced
> that allows all devices/buses on the bus/device to be reset using a depth
> first transversal.
>
> N.B. we have to expose the implicit system bus because we have various 
> hacks
> that result in an implicit system bus existing. Instead, we ought to 
> have an
> explicitly created system bus that we can trigger reset from. That's a 
> topic
> for a future patch though.
>
> Signed-off-by: Anthony Liguori <address@hidden>
> Signed-off-by: Isaku Yamahata <address@hidden>
> ---
> hw/qdev.c | 28 +++++++++++++++++++---------
> hw/qdev.h | 4 ++++
> vl.c | 1 +
> 3 files changed, 24 insertions(+), 9 deletions(-)


This patch (which is included in qemu master now) introduces
two regressions at least for MIPS system emulation:

The emulated MIPS machines mipssim and malta no longer work
because qemu tries a null pointer read access (caused by
sysbus_get_default returning NULL). Just run any of these
machines (big or little endian, 32 or 64 bit) with any mips
kernel or bios to get this crash.

This first regression can be fixed with a patch which I have
sent to qemu-devel.

The second regression also occurs with MIPS malta.
Networking no longer works with the default pcnet nic.

This is caused because the reset function for pcnet is no
longer called during system boot. The result in an invalid
mac address (all zero) and a non-working nic.

For this second regression I still have no simple solution.
Of course mips_malta.c should be converted to qdev which
would fix both problems (but only for malta system emulation).

Maybe other systems / devices don't get their reset functions
called during system boot, too.

Stefan Weil


> diff --git a/hw/qdev.c b/hw/qdev.c
> index 11d845a..92ccc8d 100644
> --- a/hw/qdev.c
> +++ b/hw/qdev.c
> @@ -257,13 +257,6 @@ DeviceState *qdev_device_add(QemuOpts *opts)
> return qdev;
> }
>
> -static void qdev_reset(void *opaque)
> -{
> - DeviceState *dev = opaque;
> - if (dev->info->reset)
> - dev->info->reset(dev);
> -}
> -
> /* Initialize a device. Device properties should be set before calling
> this function. IRQs and MMIO regions should be connected/mapped after
> calling this function.
> @@ -279,7 +272,6 @@ int qdev_init(DeviceState *dev)
> qdev_free(dev);
> return rc;
> }
> - qemu_register_reset(qdev_reset, dev);
> if (dev->info->vmsd) {
> vmstate_register_with_alias_id(dev, -1, dev->info->vmsd, dev,
> dev->instance_id_alias,
> @@ -308,6 +300,25 @@ int qdev_unplug(DeviceState *dev)
> return dev->info->unplug(dev);
> }
>
> +static int qdev_reset_one(DeviceState *dev, void *opaque)
> +{
> + if (dev->info->reset) {
> + dev->info->reset(dev);
> + }
> +
> + return 0;
> +}
> +
> +BusState *sysbus_get_default(void)
> +{
> + return main_system_bus;
> +}
> +
> +void qbus_reset_all(BusState *bus)
> +{
> + qbus_walk_children(bus, qdev_reset_one, NULL, NULL);
> +}
> +
> /* can be used as ->unplug() callback for the simple cases */
> int qdev_simple_unplug_cb(DeviceState *dev)
> {
> @@ -351,7 +362,6 @@ void qdev_free(DeviceState *dev)
> if (dev->opts)
> qemu_opts_del(dev->opts);
> }
> - qemu_unregister_reset(qdev_reset, dev);
> QLIST_REMOVE(dev, sibling);
> for (prop = dev->info->props; prop && prop->name; prop++) {
> if (prop->info->free) {
> diff --git a/hw/qdev.h b/hw/qdev.h
> index 550fd9b..e5ed333 100644
> --- a/hw/qdev.h
> +++ b/hw/qdev.h
> @@ -187,10 +187,14 @@ int qbus_walk_children(BusState *bus, 
> qdev_walkerfn *devfn,
> qbus_walkerfn *busfn, void *opaque);
> int qdev_walk_children(DeviceState *dev, qdev_walkerfn *devfn,
> qbus_walkerfn *busfn, void *opaque);
> +void qbus_reset_all(BusState *bus);
> void qbus_free(BusState *bus);
>
> #define FROM_QBUS(type, dev) DO_UPCAST(type, qbus, dev)
>
> +/* This should go away once we get rid of the NULL bus hack */
> +BusState *sysbus_get_default(void);
> +
> /*** monitor commands ***/
>
> void do_info_qtree(Monitor *mon);
> diff --git a/vl.c b/vl.c
> index c58583d..135fdeb 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -2976,6 +2976,7 @@ int main(int argc, char **argv, char **envp)
> exit(1);
> }
>
> + qemu_register_reset((void *)qbus_reset_all, sysbus_get_default());
> qemu_system_reset();
> if (loadvm) {
> if (load_vmstate(loadvm) < 0) {