path: root/kernel/irq
diff options
authorThomas Gleixner <tglx@linutronix.de>2020-08-26 13:16:32 +0200
committerThomas Gleixner <tglx@linutronix.de>2020-09-16 16:52:28 +0200
commit13b90cadfc294718dd5a89e1fcf103477b01eb50 (patch)
treec8cac2bdd4fafea7e482852b7d47b8fced59afe0 /kernel/irq
parent585dfe8abc4460810c07114b64aca10a74fa2718 (diff)
genirq/chip: Use the first chip in irq_chip_compose_msi_msg()
The documentation of irq_chip_compose_msi_msg() claims that with hierarchical irq domains the first chip in the hierarchy which has an irq_compose_msi_msg() callback is chosen. But the code just keeps iterating after it finds a chip with a compose callback. The x86 HPET MSI implementation relies on that behaviour, but that does not make it more correct. The message should always be composed at the domain which manages the underlying resource (e.g. APIC or remap table) because that domain knows about the required layout of the message. On X86 the following hierarchies exist: 1) vector -------- PCI/MSI 2) vector -- IR -- PCI/MSI The vector domain has a different message format than the IR (remapping) domain. So obviously the PCI/MSI domain can't compose the message without having knowledge about the parent domain, which is exactly the opposite of what hierarchical domains want to achieve. X86 actually has two different PCI/MSI chips where #1 has a compose callback and #2 does not. #2 delegates the composition to the remap domain where it belongs, but #1 does it at the PCI/MSI level. For the upcoming device MSI support it's necessary to change this and just let the first domain which can compose the message take care of it. That way the top level chip does not have to worry about it and the device MSI code does not need special knowledge about topologies. It just sets the compose callback to NULL and lets the hierarchy pick the first chip which has one. Due to that the attempt to move the compose callback from the direct delivery PCI/MSI domain to the vector domain made the system fail to boot with interrupt remapping enabled because in the remapping case irq_chip_compose_msi_msg() keeps iterating and choses the compose callback of the vector domain which obviously creates the wrong format for the remap table. Break out of the loop when the first irq chip with a compose callback is found and fixup the HPET code temporarily. That workaround will be removed once the direct delivery compose callback is moved to the place where it belongs in the vector domain. Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20200826112331.047917603@linutronix.de
Diffstat (limited to 'kernel/irq')
2 files changed, 13 insertions, 5 deletions
diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
index 857f5f4c8098..0ae308efa604 100644
--- a/kernel/irq/chip.c
+++ b/kernel/irq/chip.c
@@ -1541,18 +1541,17 @@ EXPORT_SYMBOL_GPL(irq_chip_release_resources_parent);
int irq_chip_compose_msi_msg(struct irq_data *data, struct msi_msg *msg)
- struct irq_data *pos = NULL;
+ struct irq_data *pos;
- for (; data; data = data->parent_data)
+ for (pos = NULL; !pos && data; data = irqd_get_parent_data(data)) {
if (data->chip && data->chip->irq_compose_msi_msg)
pos = data;
+ }
if (!pos)
return -ENOSYS;
pos->chip->irq_compose_msi_msg(pos, msg);
return 0;
diff --git a/kernel/irq/internals.h b/kernel/irq/internals.h
index 7db284b10ac9..54363527feea 100644
--- a/kernel/irq/internals.h
+++ b/kernel/irq/internals.h
@@ -473,6 +473,15 @@ static inline void irq_domain_deactivate_irq(struct irq_data *data)
+static inline struct irq_data *irqd_get_parent_data(struct irq_data *irqd)
+ return irqd->parent_data;
+ return NULL;
#include <linux/debugfs.h>