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

[Suravee Suthikulpanit]

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@xxxxxxxxxxxxxxx>
> > > ---
> > > 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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