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

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Date:   Wed, 26 Jul 2017 09:00:40 +0100
From:   Marc Zyngier <marc.zyngier@....com>
To:     Hanjun Guo <hanjun.guo@...aro.org>,
        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 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.

>>
>>>   	node = acpi_map_pxm_to_node(its_affinity->proximity_domain);
>>>   
>>>   	if (node == NUMA_NO_NODE || node >= MAX_NUMNODES) {
>>> @@ -1901,14 +1904,35 @@ static int __init gic_acpi_parse_srat_its(struct acpi_subtable_header *header,
>>>   
>>>   static void __init acpi_table_parse_srat_its(void)
>>>   {
>>> +	int count;
>>> +
>>> +	count = acpi_table_parse_entries(ACPI_SIG_SRAT,
>>> +			sizeof(struct acpi_table_srat),
>>> +			ACPI_SRAT_TYPE_GIC_ITS_AFFINITY,
>>> +			gic_acpi_match_srat_its, 0);
>>> +	if (count <= 0)
>>> +		return;
>>> +
>>> +	its_srat_maps = kmalloc(count * sizeof(struct its_srat_map),
>>> +				GFP_KERNEL);
>>> +	if (!its_srat_maps)
>>> +		return;
>>
>> and here silently returning when failing to allocate the memory. I think
>> it'd be worth having a bit of a warning.
> 
> Will do.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...