[Skiboot] [RFC PATCH 8/9] OPAL V4: initial OS-operations (traps, printf)

[Nicholas Piggin]

Excerpts from Gautham R Shenoy's message of May 6, 2020 3:37 pm:
> Hello Nicholas,
> 
> On Sat, May 02, 2020 at 09:36:48PM +1000, Nicholas Piggin wrote:
>> +static int64_t opal_register_os_ops(struct opal_os_ops *ops, uint64_t size)
>> +{
>> +	struct cpu_thread *cpu;
>> +
>> +	if (size < 8)
>> +		return OPAL_PARAMETER;
>> +
>> +	for_each_cpu(cpu) {
>> +		if (cpu == this_cpu())
>> +			continue;
>> +		if (cpu->state == cpu_state_os)
>> +			return OPAL_BUSY;
>> +	}
>> +
> 
> Is this check to ensure that the OS calls register_os_ops() before the
> secondaries are woken up?

Yes, although I'm not sure if we'd like to allow some CPUs to remain in 
skiboot. Possibly an alternative is to disallow waking more secondaries
after we set to v4.

We could let the OS synchronise this itself, but it seemed like a good 
idea for OPAL to enforce it.

> If so, when we introduce a os_stop()
> callback, it should be registered prior to idle_init() in the Kernel.

Yes I guess so.

>> +	if (opal_v4_os)
>> +		return OPAL_WRONG_STATE;
>> +
>> +	if (!verify_romem()) {
>> +		prlog(PR_NOTICE, "OPAL checksums did not match\n");
>> +		disable_fast_reboot("Inconsistent firmware romem checksum");
>> +		return OPAL_WRONG_STATE;
>> +	}
>> +
>> +	/* v4 must handle OPAL traps */
>> +	patch_traps(true);
>> +
>> +	if (size >= 8) {
>> +		os_ops.os_printf = (void *)be64_to_cpu(ops->os_printf);
>> +		set_opal_console_to_raw();
> 
> At this point, we are invoking set_opal_raw_console() only called for
> mambo_opal_raw_con, but not for uart_opal_raw_con. Do we need that if
> we want to run this series on a P9 machine ?

Hmm, good catch. I actually had it running on a P9 with lpc uart, but
possibly didn't test printing very well.

I'm not sure what to do if the driver doesn't support raw mode. Just 
disallow the register call I suppose, it's easy enough to add them.

Thanks,
Nick