[patch 04/20] genirq/irqdomain: Provide IRQ_DOMAIN_FLAG_MSI_PARENT

Thomas Gleixner
2022-11-11T14:01:04Z

The new PCI/IMS (Interrupt Message Store) functionality is allowing
hardware vendors to provide implementation specific storage for the MSI
messages. This can be device memory and also host/guest memory, e.g. in
queue memory which is shared with the hardware.

This requires device specific MSI interrupt domains, which cannot be
achived by expanding the existing PCI/MSI interrupt domain concept which is
a global interrupt domain shared by all PCI devices on a particular (IOMMU)
segment:

|--- device 1
[Vector]---[Remapping]---[PCI/MSI]--|...
|--- device N

This works because the PCI/MSI[-X] space is uniform, but falls apart with
PCI/IMS which is implementation defined and must be available along with
PCI/MSI[-X] on the same device.

To support PCI/MSI[-X] plus PCI/IMS on the same device it is required to
rework the PCI/MSI interrupt domain hierarchy concept in the following way:

|--- [PCI/MSI] device 1
[Vector]---[Remapping]---|...
|--- [PCI/MSI] device N

That allows in the next step to create multiple interrupt domains per device:

|--- [PCI/MSI] device 1
|--- [PCI/IMS] device 1
[Vector]---[Remapping]---|...
|--- [PCI/MSI] device N
|--- [PCI/IMS] device N

So the domain which previously created the global PCI/MSI domain must now
act as parent domain for the per device domains.

The hierarchy depth is the same as before, but the PCI/MSI domains are then
device specific and not longer global.

Provide IRQ_DOMAIN_FLAG_MSI_PARENT, which allows to identify these parent
domains, along with helpers to query it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
---
include/linux/irqdomain.h | 14 ++++++++++++++
1 file changed, 14 insertions(+)
--- a/include/linux/irqdomain.h
+++ b/include/linux/irqdomain.h
@@ -189,6 +189,9 @@ enum {
/* Irq domain doesn't translate anything */
IRQ_DOMAIN_FLAG_NO_MAP = (1 << 6),

+ /* Irq domain is a MSI parent domain */
+ IRQ_DOMAIN_FLAG_MSI_PARENT = (1 << 8),
+
/*
* Flags starting from IRQ_DOMAIN_FLAG_NONCORE are reserved
* for implementation specific purposes and ignored by the
@@ -551,6 +554,11 @@ static inline bool irq_domain_is_msi_rem

extern bool irq_domain_hierarchical_is_msi_remap(struct irq_domain *domain);

+static inline bool irq_domain_is_msi_parent(struct irq_domain *domain)
+{
+ return domain->flags & IRQ_DOMAIN_FLAG_MSI_PARENT;
+}
+
#else /* CONFIG_IRQ_DOMAIN_HIERARCHY */
static inline int irq_domain_alloc_irqs(struct irq_domain *domain,
unsigned int nr_irqs, int node, void *arg)
@@ -596,6 +604,12 @@ irq_domain_hierarchical_is_msi_remap(str
{
return false;
}
+
+static inline bool irq_domain_is_msi_parent(struct irq_domain *domain)
+{
+ return false;
+}
+
#endif /* CONFIG_IRQ_DOMAIN_HIERARCHY */

#else /* CONFIG_IRQ_DOMAIN */