linux-kernel - Re: [PATCH] PCI: Fix pcibios_update

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Date:	Wed, 28 Jan 2015 09:43:32 -0600
From:	Bjorn Helgaas <bhelgaas@...gle.com>
To:	Marc Zyngier <marc.zyngier@....com>
Cc:	Jiang Liu <jiang.liu@...ux.intel.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Lorenzo Pieralisi <Lorenzo.Pieralisi@....com>,
	Andre Przywara <Andre.Przywara@....com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] PCI: Fix pcibios_update_irq misuse of irq number

On Wed, Jan 28, 2015 at 9:27 AM, Marc Zyngier <marc.zyngier@....com> wrote:
> Hi Gerry,
>
> On 28/01/15 15:21, Jiang Liu wrote:
>>
>>
>> On 2015/1/28 22:51, Marc Zyngier wrote:
>>> pcibios_update_irq writes an irq number into the config space
>>> of a given PCI device, but ignores the fact that this number
>>> is a virtual interrupt number, which might be a very different
>>> value from what the underlying hardware is using.
>>>
>>> The obvious fix is to fetch the HW interrupt number from the
>>> corresponding irq_data structure. This is slightly complicated
>>> by the fact that this interrupt might be services by a stacked
>>> domain.
>>>
>>> This has been tested on KVM with kvmtool.
>>>
>>> Reported-by: Lorenzo Pieralisi <lorenzo.pieralisi@....com>
>>> Tested-by: Andre Przywara <andre.przywara@....com>
>>> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
>>> ---
>>>  drivers/pci/setup-irq.c | 12 ++++++++++--
>>>  1 file changed, 10 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/drivers/pci/setup-irq.c b/drivers/pci/setup-irq.c
>>> index 4e2d595..828cbc9 100644
>>> --- a/drivers/pci/setup-irq.c
>>> +++ b/drivers/pci/setup-irq.c
>>> @@ -15,11 +15,19 @@
>>>  #include <linux/errno.h>
>>>  #include <linux/ioport.h>
>>>  #include <linux/cache.h>
>>> +#include <linux/irq.h>
>>>
>>>  void __weak pcibios_update_irq(struct pci_dev *dev, int irq)
>>>  {
>>> -    dev_dbg(&dev->dev, "assigning IRQ %02d\n", irq);
>>> -    pci_write_config_byte(dev, PCI_INTERRUPT_LINE, irq);
>>> +    struct irq_data *d;
>>> +
>>> +    d = irq_get_irq_data(irq);
>>> +#ifdef CONFIG_IRQ_DOMAIN_HIERARCHY
>>> +    while (d->parent_data)
>>> +            d = d->parent_data;
>>> +#endif
>>> +    dev_dbg(&dev->dev, "assigning IRQ %02ld\n", d->hwirq);
>>> +    pci_write_config_byte(dev, PCI_INTERRUPT_LINE, d->hwirq);
>>>  }
>> Hi Mark,
>>       Instead of modifying the common version, how about
>> implementing an arch specific version? Arch may have different
>> way to determine the irq number. Above implementation doesn't
>> work with x86, for example.
>
> If you look at the Makefile, this file is used on:
>
> obj-$(CONFIG_ALPHA) += setup-irq.o
> obj-$(CONFIG_ARM) += setup-irq.o
> obj-$(CONFIG_UNICORE32) += setup-irq.o
> obj-$(CONFIG_SUPERH) += setup-irq.o
> obj-$(CONFIG_MIPS) += setup-irq.o
> obj-$(CONFIG_TILE) += setup-irq.o
> obj-$(CONFIG_SPARC_LEON) += setup-irq.o
> obj-$(CONFIG_M68K) += setup-irq.o
>
> x86 doesn't use that at all.

Since you're looking at this, Marc, do you see a nice way to get rid
of these arch dependencies in the Makefile and unify this a bit?  We
still have this pci_fixup_irqs() ugliness -- it's not really
arch-specific at all, but it's called from arch code, and it uses
for_each_pci_dev(), which obviously only works for things present at
boot and not for things hot-added later.

Bjorn
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