Re: [PATCH v5 09/19] arch_topology: Use the last level cache information from the cacheinfo

[Conor.Dooley]

On 30/06/2022 18:35, Sudeep Holla wrote:
> On Thu, Jun 30, 2022 at 04:37:50PM +0000, Conor.Dooley@xxxxxxxxxxxxx wrote:
>> On 30/06/2022 11:39, Sudeep Holla wrote:
>>>
>>> I can't think of any reason for that to happen unless detect_cache_attributes
>>> is failing from init_cpu_topology and we are ignoring that.
>>>
>>> Are all RISC-V platforms failing on -next or is it just this platform ?
>>
>> I don't know. I only have SoCs with this core complex & one that does not
>> work with upstream. I can try my other board with this SoC - but I am on
>> leave at the moment w/ a computer or internet during the day so it may be
>> a few days before I can try it.
>>
> 
> Sure, no worries.
> 
>> However, Niklas Cassel has tried to use the Canaan K210 on next-20220630
>> but had issues with RCU stalling:
>> https://lore.kernel.org/linux-riscv/Yr3PKR0Uj1bE5Y6O@x1-carbon/T/#m52016996fcf5fa0501066d73352ed8e806803e06
>> Not going to claim any relation, but that's minus 1 to the platforms that
>> can be used to test this on upstream RISC-V.
>>
> 
> Ah OK, will check and ask full logs to see if there is any relation.
> 
>>> We may have to try with some logs in detect_cache_attributes,
>>> last_level_cache_is_valid and last_level_cache_is_shared to check where it
>>> is going wrong.
>>>
>>> It must be crashing in smp_callin->update_siblings_masks->last_level_cache_is_shared


So, looks like there's a problem in cache_leaves_are_shared() which is hit
by the above path. Both of the if clauses are false, and the function falls
through to return sib_leaf->fw_token == this_leaf->fw_token;
Both sib_leaf & this_leaf seem to be null.

static inline bool cache_leaves_are_shared(struct cacheinfo *this_leaf,
					   struct cacheinfo *sib_leaf)
{
	/*
	 * For non DT/ACPI systems, assume unique level 1 caches,
	 * system-wide shared caches for all other levels. This will be used
	 * only if arch specific code has not populated shared_cpu_map
	 */
	if (!(IS_ENABLED(CONFIG_OF) || IS_ENABLED(CONFIG_ACPI)))
		return !(this_leaf->level == 1);

	if ((sib_leaf->attributes & CACHE_ID) &&
	    (this_leaf->attributes & CACHE_ID))
		return sib_leaf->id == this_leaf->id;

	return sib_leaf->fw_token == this_leaf->fw_token;
}

Any ideas what to look at next?