On Tue, Oct 15, 2013 at 3:47 PM, Alexey Kardashevskiy <aik@xxxxxxxxx> wrote:
> On 10/16/2013 02:03 AM, Alexander Graf wrote:
>> On 10/15/2013 10:50 AM, Alexey Kardashevskiy wrote:
>>> Old kernels (< 3.1) handle hvcX devices different in different parts.
>>> Sometime the kernel assumes that the hvc device numbers start from zero
>>> and if there is just one hvc, then it is hvc0.
>>>
>>> However kernel's add_preferred_console() uses the very last byte of
>>> the VTY's "reg" property as an hvc number so it might end up with something
>>> different than hvc.
>>>
>>> The problem appears on SLES11SP3 and RHEL6. If to run QEMU without
>>> -nodefaults, then the default VTY is created first on a VIO bus and gets
>>> reg==0x71000000 so it will be hvc0 and everything will be fine.
>>> If to run QEMU with:
>>> -nodefaults \
>>> -chardev "socket,id=char1,host=localhost,port=8001,server,telnet,mux=on" \
>>> -device "spapr-vty,chardev=char1" \
>>> -mon "chardev=char1,mode=readline,id=mon1" \
>>>
>>> then the exactly the same config is expected but in this case spapr-vty
>>> gets reg==0x71000001 and therefore it becomes hvc1 and lots of debug
>>> output is missing. SLES11SP3 does not even boot as /dev/console is
>>> redirected to /dev/hvc0 which is dead.
>>>
>>> The issue can be solved by manual selection of VTY's "reg" property to
>>> have last byte equal to zero.
>>>
>>> The alternative would be to use separate "reg" property counter for
>>> automatic "reg" property generation and this is what the patch does.
>>>
>>> Signed-off-by: Alexey Kardashevskiy<aik@xxxxxxxxx>
>>> ---
>>>
>>> Since libvirt uses "-nodefault" a lot and in this case "spapr-nvram" gets
>>> created first and gets reg=0x71000000, we cannot just ignore this. Also,
>>> it does not seem an option to require libvirt users to specify spapr-vty
>>> "reg" property every time.
>>>
>>> Can anyone think of a simpler solutionu? Thanks.
>>>
>>>
>>> ---
>>> hw/ppc/spapr_vio.c | 7 ++++++-
>>> include/hw/ppc/spapr_vio.h | 1 +
>>> 2 files changed, 7 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/hw/ppc/spapr_vio.c b/hw/ppc/spapr_vio.c
>>> index a6a0a51..2d56950 100644
>>> --- a/hw/ppc/spapr_vio.c
>>> +++ b/hw/ppc/spapr_vio.c
>>> @@ -438,7 +438,11 @@ static int spapr_vio_busdev_init(DeviceState *qdev)
>>> VIOsPAPRBus *bus = DO_UPCAST(VIOsPAPRBus, bus,
>>> dev->qdev.parent_bus);
>>>
>>> do {
>>> - dev->reg = bus->next_reg++;
>>> + if (!object_dynamic_cast(OBJECT(qdev), "spapr-vty")) {
>>> + dev->reg = bus->next_reg++;
>>> + } else {
>>> + dev->reg = bus->next_vty_reg++;
>>> + }
>>> } while (reg_conflict(dev));
>>> }
>>>
>>> @@ -501,6 +505,7 @@ VIOsPAPRBus *spapr_vio_bus_init(void)
>>> qbus = qbus_create(TYPE_SPAPR_VIO_BUS, dev, "spapr-vio");
>>> bus = DO_UPCAST(VIOsPAPRBus, bus, qbus);
>>> bus->next_reg = 0x71000000;
>>> + bus->next_vty_reg = 0x71000100;
>>
>> This breaks as soon as you pass in more than 0x100 devices that are non-vty
>> into the guest, no?
>
> Will we ever have this much? Ah, anyway, this code already checks if the
> address is taken and fails if it is. And there is still a possibility to
> assign addresses manually.
>
>> The reg property really describes the virtual slot a device is in.
>
> We use 0x71000000. I saw xmls from libvirt where VTY's reg is 0x30000000.
> Whether it is a slot or not, QEMU/SLOF/Kernel does not seem to care about
> absolute value :)
>
>> Couldn't
>> we do that allocation explicitly and push it from libvirt, just like we do
>> it with the slots for PCI?
Yes, this is the only solution. We make no promises with respect to
argument ordering. libvirt needs to explicitly specify reg values to
create a stable device tree (just like it does with PCI).
Regards,
Anthony Liguori
>
> That is the other possibility, yes. But in this case "-nodefaults" must not
> create spapr-nvram automatically and if we do that, we'll break existing
> setups.
>
>
>>
>>
>> Alex
>>
>>
>>>
>>> /* hcall-vio */
>>> spapr_register_hypercall(H_VIO_SIGNAL, h_vio_signal);
>>> diff --git a/include/hw/ppc/spapr_vio.h b/include/hw/ppc/spapr_vio.h
>>> index d8b3b03..3a92d9e 100644
>>> --- a/include/hw/ppc/spapr_vio.h
>>> +++ b/include/hw/ppc/spapr_vio.h
>>> @@ -73,6 +73,7 @@ struct VIOsPAPRDevice {
>>> struct VIOsPAPRBus {
>>> BusState bus;
>>> uint32_t next_reg;
>>> + uint32_t next_vty_reg;
>>> int (*init)(VIOsPAPRDevice *dev);
>>> int (*devnode)(VIOsPAPRDevice *dev, void *fdt, int node_off);
>>> };
>>
>
>
> --
> Alexey
>
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