On 29/09/17 21:52, Nikunj A Dadhania wrote:
> David Gibson <[email protected]> writes:
>
>> On Thu, Sep 28, 2017 at 04:07:38PM +0530, Aravinda Prasad wrote:
>>> Receive updates from SLOF about the updated rtas-base.
>>> A separate patch for SLOF [1] (commit f9a60de3) adds
>>> functionality to invoke a private HCALL whenever OS
>>> issues instantiate-rtas with a new rtas-base.
>>>
>>> This is required as QEMU needs to know the updated rtas-base
>>> as it allocates error reporting structure in RTAS space upon
>>> a machine check exception.
>>>
>>> [1] https://lists.ozlabs.org/pipermail/linuxppc-dev/2014-August/120386.html
>>>
>>> Signed-off-by: Aravinda Prasad <[email protected]>
>>> Reviewed-by: David Gibson <[email protected]>
>>
>> Ao I acked this earlier, but I've now realized there might be some
>> connection between this and discussions taking place elsewhere about
>> qemu not knowing what SLOF does with the device tree.
>>
>> At what point will SLOF call the UPDATE_RTAS hcall? I'm guessing at
>> the time of instantiate-rtas, is that right?
>
> The call happens from
> arch/powerpc/kernel/prom_init.c:prom_instantiate_rtas() and after that
> linux kernel makes two entries in the DT
>
> ....
> if (call_prom_ret("call-method", 3, 2, &entry,
> ADDR("instantiate-rtas"),
> rtas_inst, base) != 0
> || entry == 0) {
> prom_printf(" failed\n");
> return;
> }
> prom_printf(" done\n");
>
> reserve_mem(base, size);
>
> val = cpu_to_be32(base);
> prom_setprop(rtas_node, "/rtas", "linux,rtas-base",
> &val, sizeof(val));
> val = cpu_to_be32(entry);
> prom_setprop(rtas_node, "/rtas", "linux,rtas-entry",
> &val, sizeof(val));
> ....
>
> Quiesce is called after this.
>
>> Does SLOF put the RTAS blob address in its internal device tree, or
>> does it only pass it to the guest via the return parameters from
>> instantiate-rtas?
>
> Entry was made to the DT by linux kernel prom_init code, will this be
> visible to QEMU?
With my recent SLOF FDT patch - yes:
aik@fstn1-p1:~$ grep rtas dbg.dts
rtas {
linux,rtas-entry = <0x2fff0000>;
linux,rtas-base = <0x2fff0000>;
[...]
--
Alexey
