[PATCH v2 6/9] irqchip/msi-lib: Honour the MSI_FLAG_NO_AFFINITY flag
From: Marc Zyngier <maz@kernel.org>
Date: 2025-05-13 17:28:31
Also in:
linux-pci, lkml
Subsystem:
irqchip drivers, the rest · Maintainers:
Thomas Gleixner, Linus Torvalds
Bad MSI implementations multiplex MSIs onto a single downstream interrupt, meaning they have no concept of individual affinity. The old MSI code did a reasonable job at this by honouring the MSI_FLAG_NO_AFFINITY, but the new shiny device MSI code doesn't. Teach it about the sad reality of existing hardware. Signed-off-by: Marc Zyngier <maz@kernel.org> --- drivers/irqchip/irq-msi-lib.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/irqchip/irq-msi-lib.c b/drivers/irqchip/irq-msi-lib.c
index 2a61c06c4da07..246c30205af40 100644
--- a/drivers/irqchip/irq-msi-lib.c
+++ b/drivers/irqchip/irq-msi-lib.c@@ -105,8 +105,13 @@ bool msi_lib_init_dev_msi_info(struct device *dev, struct irq_domain *domain, * MSI message into the hardware which is the whole purpose of the * device MSI domain aside of mask/unmask which is provided e.g. by * PCI/MSI device domains. + * + * The exception to the rule is when the underlying domain + * tells you that affinity is not a thing -- for example when + * everything is muxed behind a single interrupt. */ - chip->irq_set_affinity = msi_domain_set_affinity; + if (!chip->irq_set_affinity && !(info->flags & MSI_FLAG_NO_AFFINITY)) + chip->irq_set_affinity = msi_domain_set_affinity; return true; } EXPORT_SYMBOL_GPL(msi_lib_init_dev_msi_info);
--
2.39.2