linux-kernel - Re: [PATCH v2] irqchip/gic-v3-its: Allow GIC ITS number more than MAX

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Message-ID: <5db70933-807a-fba1-2f36-94c6b361c4cd@linaro.org>
Date:   Wed, 26 Jul 2017 18:03:28 +0800
From:   Hanjun Guo <hanjun.guo@...aro.org>
To:     Marc Zyngier <marc.zyngier@....com>,
        Hanjun Guo <guohanjun@...wei.com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     linux-acpi@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, linuxarm@...wei.com,
        Ganapatrao Kulkarni <ganapatrao.kulkarni@...ium.com>,
        Lorenzo Pieralisi <lorenzo.pieralisi@....com>
Subject: Re: [PATCH v2] irqchip/gic-v3-its: Allow GIC ITS number more than
 MAX_NUMNODES

On 2017/7/26 18:01, Marc Zyngier wrote:
> On 26/07/17 10:55, Hanjun Guo wrote:
>> On 2017/7/26 16:00, Marc Zyngier wrote:
>>> On 26/07/17 08:52, Hanjun Guo wrote:
>>>> On 2017/7/25 18:30, Marc Zyngier wrote:
>>>>> On 22/07/17 04:54, Hanjun Guo wrote:
>>>>>> From: Hanjun Guo <hanjun.guo@...aro.org>
>>>>>>
>>>>>> When running 4.13-rc1 on top of D05, I got the boot log:
>>>>>>
>>>>>> [    0.000000] SRAT: PXM 0 -> ITS 0 -> Node 0
>>>>>> [    0.000000] SRAT: PXM 0 -> ITS 1 -> Node 0
>>>>>> [    0.000000] SRAT: PXM 0 -> ITS 2 -> Node 0
>>>>>> [    0.000000] SRAT: PXM 1 -> ITS 3 -> Node 1
>>>>>> [    0.000000] SRAT: ITS affinity exceeding max count[4]
>>>>>>
>>>>>> This is wrong on D05 as we have 8 ITSes with 4 NUMA nodes.
>>>>>>
>>>>>> So dynamically alloc the memory needed instead of using
>>>>>> its_srat_maps[MAX_NUMNODES], which count the number of
>>>>>> ITS entry(ies) in SRAT and alloc its_srat_maps as needed,
>>>>>> then build the mapping of numa node to ITS ID. Of course,
>>>>>> its_srat_maps will be freed after ITS probing because
>>>>>> we don't need that after boot.
>>>>>>
>>>>>> After doing this, I got what I wanted:
>>>>>>
>>>>>> [    0.000000] SRAT: PXM 0 -> ITS 0 -> Node 0
>>>>>> [    0.000000] SRAT: PXM 0 -> ITS 1 -> Node 0
>>>>>> [    0.000000] SRAT: PXM 0 -> ITS 2 -> Node 0
>>>>>> [    0.000000] SRAT: PXM 1 -> ITS 3 -> Node 1
>>>>>> [    0.000000] SRAT: PXM 2 -> ITS 4 -> Node 2
>>>>>> [    0.000000] SRAT: PXM 2 -> ITS 5 -> Node 2
>>>>>> [    0.000000] SRAT: PXM 2 -> ITS 6 -> Node 2
>>>>>> [    0.000000] SRAT: PXM 3 -> ITS 7 -> Node 3
>>>>>>
>>>>>> Fixes: dbd2b8267233 ("irqchip/gic-v3-its: Add ACPI NUMA node mapping")
>>>>>> Signed-off-by: Hanjun Guo <hanjun.guo@...aro.org>
>>>>>> Cc: Ganapatrao Kulkarni <ganapatrao.kulkarni@...ium.com>
>>>>>> Cc: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
>>>>>> Cc: Marc Zyngier <marc.zyngier@....com>
>>>>>> ---
>>>>>>
>>>>>> v1->v2:
>>>>>>      - Add NULL check in acpi_get_its_numa_node() for no ITS affinity case;
>>>>>>      - Free the its_srat_maps after ITS probing.
>>>>>>
>>>>>>     drivers/irqchip/irq-gic-v3-its.c | 39 ++++++++++++++++++++++++++++++++-------
>>>>>>     1 file changed, 32 insertions(+), 7 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/irqchip/irq-gic-v3-its.c b/drivers/irqchip/irq-gic-v3-its.c
>>>>>> index 3ccdf76..1d692aa 100644
>>>>>> --- a/drivers/irqchip/irq-gic-v3-its.c
>>>>>> +++ b/drivers/irqchip/irq-gic-v3-its.c
>>>>>> @@ -1847,13 +1847,16 @@ struct its_srat_map {
>>>>>>     	u32	its_id;
>>>>>>     };
>>>>>>     
>>>>>> -static struct its_srat_map its_srat_maps[MAX_NUMNODES] __initdata;
>>>>>> +static struct its_srat_map *its_srat_maps __initdata;
>>>>>>     static int its_in_srat __initdata;
>>>>>>     
>>>>>>     static int __init acpi_get_its_numa_node(u32 its_id)
>>>>>>     {
>>>>>>     	int i;
>>>>>>     
>>>>>> +	if (!its_srat_maps)
>>>>>> +		return NUMA_NO_NODE;
>>>>>> +
>>>>>>     	for (i = 0; i < its_in_srat; i++) {
>>>>>>     		if (its_id == its_srat_maps[i].its_id)
>>>>>>     			return its_srat_maps[i].numa_node;
>>>>>> @@ -1861,6 +1864,12 @@ static int __init acpi_get_its_numa_node(u32 its_id)
>>>>>>     	return NUMA_NO_NODE;
>>>>>>     }
>>>>>>     
>>>>>> +static int __init gic_acpi_match_srat_its(struct acpi_subtable_header *header,
>>>>>> +					  const unsigned long end)
>>>>>> +{
>>>>>> +	return 0;
>>>>>> +}
>>>>>> +
>>>>>>     static int __init gic_acpi_parse_srat_its(struct acpi_subtable_header *header,
>>>>>>     			 const unsigned long end)
>>>>>>     {
>>>>>> @@ -1877,12 +1886,6 @@ static int __init gic_acpi_parse_srat_its(struct acpi_subtable_header *header,
>>>>>>     		return -EINVAL;
>>>>>>     	}
>>>>>>     
>>>>>> -	if (its_in_srat >= MAX_NUMNODES) {
>>>>>> -		pr_err("SRAT: ITS affinity exceeding max count[%d]\n",
>>>>>> -				MAX_NUMNODES);
>>>>>> -		return -EINVAL;
>>>>>> -	}
>>>>>> -
>>>>>
>>>>> So you're getting rid of that message when overflowing the array...
>>>>
>>>> This overflowing will not happen, because I scan the SRAT
>>>> to count the entry(ies) of ITS affinity first to alloc the
>>>> array, and then parse the same SRAT again to setup the mapping
>>>> of NUMA node to ITS, so is it fine for us to just remove the
>>>> check here?
>>>
>>> Removing that check is fine, as long as you make sure the allocation
>>> hasn't failed.
>>
>> Sorry, just want to make sure I understand correctly. This function will
>> not be called if allocation failure, so do you mean we can keep the code
>> as it is?
> 
> No. I mean adding this warning when the allocation fails, so that we
> know that our NUMA topology is screwed.

OK, thanks!

Hanjun