Re: [PATCH] irqchip, gicv3-its, numa: Workaround for Cavium ThunderX erratum 23144

From: Ganapatrao Kulkarni
Date: Mon Aug 24 2015 - 12:28:59 EST

Hi Marc,

thanks for the suggestions.

On Mon, Aug 24, 2015 at 7:17 PM, Marc Zyngier <marc.zyngier@xxxxxxx> wrote:
> On 24/08/15 14:27, Ganapatrao Kulkarni wrote:
>> On Mon, Aug 24, 2015 at 6:15 PM, Marc Zyngier <marc.zyngier@xxxxxxx> wrote:
>>>>>> static void its_enable_cavium_thunderx(void *data)
>>>>>> {
>>>>>> - struct its_node *its = data;
>>>>>> + struct its_node __maybe_unused *its = data;
>>>>>> - its->flags |= ITS_FLAGS_CAVIUM_THUNDERX;
>>>>>> +#ifdef CONFIG_CAVIUM_ERRATUM_22375
>>>>>> + its->flags |= ITS_WORKAROUND_CAVIUM_22375;
>>>>>> + pr_info("ITS: Enabling workaround for 22375, 24313\n");
>>>>>> +#endif
>>>>>> +
>>>>>> +#ifdef CONFIG_CAVIUM_ERRATUM_23144
>>>>>> + if (num_possible_nodes() > 1) {
>>>>>> + its->numa_node = its_get_node_thunderx(its);
>>>>> I'd rather see numa_node being always initialized to something useful.
>>>>> If you're adding numa support, why can't this be initialized via
>>>>> standard topology bindings?
>>>> IIUC, topology defines only cpu topology.
>>> Well, welcome to a much more complex system where both your CPUs and
>>> your IOs have some degree of affinity. This needs to be described
>>> properly, and not hacked on the side.
>> ok, will add description for the function.
> I sense that you misunderstood what I meant. What I'd like to see is
> some topology information coming from DT, showing the relationship
> between a device (your ITS) and a given node (your socket). This can
> then be used from two purposes:
sure will post next version with changes as per you comments.
> - find the optimal affinity for a MSI so that it doesn't default to a
> foreign node (a reasonable performance expectation),
this can be done by adding dt associativity property to its node.
i can send in next version of patch.
> - work around implementation bugs where an LPI cannot be routed to a
> redistributor that is on a foreign node.

> I really don't feel like adding a hack just for the second point, and
> I'd rather get the big picture right so that your workaround is just a
> special case of the generic one.
> Thanks,
> M.
> --
> Jazz is not dead. It just smells funny...

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