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SubjectRe: [Bugfix 1/2] ACPI, PCI, irq: Do not share PCI IRQ with ISA IRQ
On Thu, Sep 17, 2015 at 02:02:45PM +0800, Jiang Liu wrote:
> Avoid IRQs occupied by ISA IRQs when allocating IRQs for PCI link devices,
> otherwise it may cause interrupt storm due to incompatible pin attributes.
>
> This issue was triggered on a KVM virtual machine, which
> 1) uses IRQ9 for SCI in high level mode.
> 2) defines an PCI interrupt link device (LNKS) with IRQ9 as the only
> possible irq.
> 3) has an PCI device referring to link device LNKS.
> So it causes interrupt storm when enabling the PCI device because PCI IRQ
> works in low level mode.
>
> Signed-off-by: Jiang Liu <jiang.liu@linux.intel.com>

Acked-by: Bjorn Helgaas <bhelgaas@google.com>

> ---
> drivers/acpi/pci_irq.c | 1 +
> drivers/acpi/pci_link.c | 13 +++++++++++++
> include/linux/acpi.h | 1 +
> 3 files changed, 15 insertions(+)
>
> diff --git a/drivers/acpi/pci_irq.c b/drivers/acpi/pci_irq.c
> index 6da0f9beab19..c9336751e5e3 100644
> --- a/drivers/acpi/pci_irq.c
> +++ b/drivers/acpi/pci_irq.c
> @@ -372,6 +372,7 @@ static int acpi_isa_register_gsi(struct pci_dev *dev)
>
> /* Interrupt Line values above 0xF are forbidden */
> if (dev->irq > 0 && (dev->irq <= 0xF) &&
> + acpi_isa_irq_available(dev->irq) &&
> (acpi_isa_irq_to_gsi(dev->irq, &dev_gsi) == 0)) {
> dev_warn(&dev->dev, "PCI INT %c: no GSI - using ISA IRQ %d\n",
> pin_name(dev->pin), dev->irq);
> diff --git a/drivers/acpi/pci_link.c b/drivers/acpi/pci_link.c
> index 3b4ea98e3ea0..246e50d22120 100644
> --- a/drivers/acpi/pci_link.c
> +++ b/drivers/acpi/pci_link.c
> @@ -553,6 +553,13 @@ static int acpi_pci_link_allocate(struct acpi_pci_link *link)
> irq = link->irq.possible[i];
> }
> }
> + if (acpi_irq_penalty[irq] >= PIRQ_PENALTY_ISA_ALWAYS) {
> + printk(KERN_ERR PREFIX "No IRQ available for %s [%s]. "
> + "Try pci=noacpi or acpi=off\n",
> + acpi_device_name(link->device),
> + acpi_device_bid(link->device));
> + return -ENODEV;
> + }
>
> /* Attempt to enable the link device at this IRQ. */
> if (acpi_pci_link_set(link, irq)) {
> @@ -821,6 +828,12 @@ void acpi_penalize_isa_irq(int irq, int active)
> }
> }
>
> +bool acpi_isa_irq_available(int irq)
> +{
> + return irq >= 0 && (irq >= ARRAY_SIZE(acpi_irq_penalty) ||
> + acpi_irq_penalty[irq] < PIRQ_PENALTY_ISA_ALWAYS);
> +}
> +
> /*
> * Penalize IRQ used by ACPI SCI. If ACPI SCI pin attributes conflict with
> * PCI IRQ attributes, mark ACPI SCI as ISA_ALWAYS so it won't be use for
> diff --git a/include/linux/acpi.h b/include/linux/acpi.h
> index 7235c4851460..43856d19cf4d 100644
> --- a/include/linux/acpi.h
> +++ b/include/linux/acpi.h
> @@ -217,6 +217,7 @@ struct pci_dev;
>
> int acpi_pci_irq_enable (struct pci_dev *dev);
> void acpi_penalize_isa_irq(int irq, int active);
> +bool acpi_isa_irq_available(int irq);
> void acpi_penalize_sci_irq(int irq, int trigger, int polarity);
> void acpi_pci_irq_disable (struct pci_dev *dev);
>
> --
> 1.7.10.4
>
> --
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