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Subject[PATCH] PCI/portdrv: Do not setup up IRQs if there are no users
Date
From: Jan Kiszka <jan.kiszka@siemens.com>

Avoid registering service IRQs if there is no service that offers them
or no driver to register a handler against them. This saves IRQ vectors
when they are limited (e.g. on x86) and also avoids that spurious events
could hit a missing handler. Such spurious events need to be generated
by the Jailhouse hypervisor for active MSI vectors when enabling or
disabling itself.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
---
drivers/pci/pcie/portdrv_core.c | 40 ++++++++++++++++++++++-----------
1 file changed, 27 insertions(+), 13 deletions(-)

diff --git a/drivers/pci/pcie/portdrv_core.c b/drivers/pci/pcie/portdrv_core.c
index e1fed6649c41..2a702ccffaac 100644
--- a/drivers/pci/pcie/portdrv_core.c
+++ b/drivers/pci/pcie/portdrv_core.c
@@ -312,7 +312,7 @@ static int pcie_device_init(struct pci_dev *pdev, int service, int irq)
*/
int pcie_port_device_register(struct pci_dev *dev)
{
- int status, capabilities, i, nr_service;
+ int status, capabilities, irq_services, i, nr_service;
int irqs[PCIE_PORT_DEVICE_MAXSERVICES];

/* Enable PCI Express port device */
@@ -326,18 +326,32 @@ int pcie_port_device_register(struct pci_dev *dev)
return 0;

pci_set_master(dev);
- /*
- * Initialize service irqs. Don't use service devices that
- * require interrupts if there is no way to generate them.
- * However, some drivers may have a polling mode (e.g. pciehp_poll_mode)
- * that can be used in the absence of irqs. Allow them to determine
- * if that is to be used.
- */
- status = pcie_init_service_irqs(dev, irqs, capabilities);
- if (status) {
- capabilities &= PCIE_PORT_SERVICE_HP;
- if (!capabilities)
- goto error_disable;
+
+ irq_services = 0;
+ if (IS_ENABLED(CONFIG_PCIE_PME))
+ irq_services |= PCIE_PORT_SERVICE_PME;
+ if (IS_ENABLED(CONFIG_PCIEAER))
+ irq_services |= PCIE_PORT_SERVICE_AER;
+ if (IS_ENABLED(CONFIG_HOTPLUG_PCI_PCIE))
+ irq_services |= PCIE_PORT_SERVICE_HP;
+ if (IS_ENABLED(CONFIG_PCIE_DPC))
+ irq_services |= PCIE_PORT_SERVICE_DPC;
+ irq_services &= capabilities;
+
+ if (irq_services) {
+ /*
+ * Initialize service irqs. Don't use service devices that
+ * require interrupts if there is no way to generate them.
+ * However, some drivers may have a polling mode (e.g.
+ * pciehp_poll_mode) that can be used in the absence of irqs.
+ * Allow them to determine if that is to be used.
+ */
+ status = pcie_init_service_irqs(dev, irqs, irq_services);
+ if (status) {
+ irq_services &= PCIE_PORT_SERVICE_HP;
+ if (!irq_services)
+ goto error_disable;
+ }
}

/* Allocate child services if any */
--
2.31.1
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