linux-kernel - Re: [Patch Part2 v5 21/31] PCI/MSI: Enhance core to support hierarchy irqdomain

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Date:	Mon, 10 Nov 2014 09:03:53 +0700
From:	Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
To:	Jiang Liu <jiang.liu@...ux.intel.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Randy Dunlap <rdunlap@...radead.org>,
	Yinghai Lu <yinghai@...nel.org>,
	Borislav Petkov <bp@...en8.de>,
	Grant Likely <grant.likely@...aro.org>,
	Marc Zyngier <marc.zyngier@....com>,
	Yingjoe Chen <yingjoe.chen@...iatek.com>,
	"Matthias Brugger" <matthias.bgg@...il.com>,
	Yijing Wang <wangyijing@...wei.com>,
	Alexander Gordeev <agordeev@...hat.com>
CC:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Tony Luck <tony.luck@...el.com>,
	Joerg Roedel <joro@...tes.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	<x86@...nel.org>, <linux-kernel@...r.kernel.org>,
	<linux-pci@...r.kernel.org>, <linux-acpi@...r.kernel.org>,
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [Patch Part2 v5 21/31] PCI/MSI: Enhance core to support hierarchy
 irqdomain

On 11/9/14 14:15, Jiang Liu wrote:
> On 2014/11/9 12:26, Suravee Suthikulpanit wrote:
>> Hi Gerry,
>>
>> Please see my comments / questions below.
>>
>> On 11/6/14 21:20, Jiang Liu wrote:
>>> Enhance PCI MSI core to support hierarchy irqdomain, so the common
>>> code could be shared among architectures.
>>>
>>> Signed-off-by: Jiang Liu <jiang.liu@...ux.intel.com>
>>> ---
>>> Hi Thomas,
>>>      These changes are a temporary solution, I'm working on another
>>> patch set which will refine these interfaces, especially kill
>>> arch_msi_irq_domain_{set|get}_hwirq().
>>> Regards!
>>> Gerry
>>
>> Would the change includes the struct irqdomain_msi_data proposed by
>> Thomas here (https://lkml.org/lkml/2014/11/6/210)?
> Hi Suravee,
> 	I'm working on another patch set which will refine the way to
> create irqdomain for MSI. I hope will solve all issues mentioned by
> Thomas. I will post that patch set as RFC within one or two days.

Let me know if I can help.

>>
>>> [...]
>>> +static int msi_domain_alloc(struct irq_domain *domain, unsigned int
>>> virq,
>>> +                unsigned int nr_irqs, void *arg)
>>> +{
>>> +    int i, ret;
>>> +    irq_hw_number_t hwirq = arch_msi_irq_domain_get_hwirq(arg);
>>> +
>>> +    if (irq_find_mapping(domain, hwirq) > 0)
>>> +        return -EEXIST;
>>> +
>>> +    ret = irq_domain_alloc_irqs_parent(domain, virq, nr_irqs, arg);
>>> +    if (ret < 0)
>>> +        return ret;
>>> +
>>
>> When executing irq_domain_alloc_irqs_parent(), it triggers the following
>> warning message due to
>>
>>      WARN_ON(desc->irq_data.chip == &no_irq_chip)
>>
>> ------------[ cut here ]------------
>> WARNING: CPU: 2 PID: 912 at kernel/irq/chip.c:734
>> __irq_set_handler+0x138/0x13c()
>> Modules linked in: mlx4_core(+) rtc_efi efivarfs
>> CPU: 2 PID: 912 Comm: modprobe Not tainted 3.18.0-rc3-p2v5+ #53
>> Call trace:
>> [<fffffe00000963d4>] dump_backtrace+0x0/0x16c
>> [<fffffe0000096550>] show_stack+0x10/0x1c
>> [<fffffe000067545c>] dump_stack+0x74/0x98
>> [<fffffe00000b205c>] warn_slowpath_common+0x84/0xac
>> [<fffffe00000b2148>] warn_slowpath_null+0x14/0x20
>> [<fffffe00000ed968>] __irq_set_handler+0x134/0x13c
>> [<fffffe000042af14>] gic_irq_domain_map+0x4c/0xac
>> [<fffffe000042afd4>] gic_irq_domain_alloc+0x60/0x88
>> [<fffffe000042b374>] gicv2m_domain_alloc+0x30/0xa8
>> [<fffffe00000efc1c>] __irq_domain_alloc_irqs+0x144/0x30c
>> [<fffffe000042b58c>] gicv2m_setup_msi_irq+0xc0/0x118
>> [<fffffe000044548c>] arch_setup_msi_irq+0x34/0x60
>> [<fffffe0000445544>] arch_setup_msi_irqs+0x50/0xb0
>> [<fffffe0000445e3c>] pci_enable_msix+0x310/0x39c
>> [<fffffe0000445efc>] pci_enable_msix_range+0x34/0x9c
>> ....
>>
>> However, I think if we call irq_domain_set_hwirq_and_chip() in the
>> msi_create_irq_domain() as suggested by Thomas, that should also fix
>> this issue.
> We didn't trigger this warning on x86 because only the outer-most
> irqdomain will set irq flow handler. On ARM, the inner GIC domain
> will set irq flow handler, but the irq_data->chip for outer-most
> domain hasn't been set yet.
>
> I'm still find a way out here. Maybe we need to relax the WARN_ON().

What if we just switch the order and call the 
irq_domain_alloc_irqs_parent() after the loop? That way we can still 
keep the WARN_ON().

Suravee
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