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irqchip/msi-lib: Honour the MSI_FLAG_NO_AFFINITY flag 

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>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/all/20250513172819.2216709-7-maz@kernel.org
This commit is contained in:
Marc Zyngier 2025-05-13 18:28:16 +01:00 committed by Thomas Gleixner
parent b35961ce0a
commit 06526443a3
1 changed files with 6 additions and 1 deletions
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7
drivers/irqchip/irq-msi-lib.c
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@ -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);