On 06.07.2016 14:17, Thomas Gleixner wrote: > On Fri, 1 Jul 2016, Alexander Popov wrote: > >> Export __irq_domain_alloc_irqs() and irq_domain_free_irqs() for being >> able to work with irq_domain hierarchy in modules. > > We usually export only when we have a proper use case which is supposed to go > into the kernel tree proper. What's yours?
Hello, Thomas, I work at Positive Technologies ( https://www.ptsecurity.com/ ). We develop a bare-metal hypervisor, which targets x86_64 and supports Linux as a guest OS. Intel VT-x allows hypervisor to inject interrupts into virtual machines. We want to handle these interrupts in guest Linux. So I wrote a simple kernel module creating an irq_domain, which has x86_vector_domain as a parent in the hierarchy. In this module I just call: - irq_domain_alloc_irqs() to allocate irqs and allow calling request_irq() for them; - irqd_cfg(irq_get_irq_data()) to get the APIC vectors of the allocated irqs; - irq_domain_free_irqs() to free the resources at the end. It allows to handle interrupts injected by the hypervisor in guest Linux easily, without emulating MSI-capable PCI device at the hypervisor side. Everything works fine if __irq_domain_alloc_irqs() and irq_domain_free_irqs() are exported. Is it a proper use-case? Do you think my module could be useful for the mainline in some form? It took me some time to understand irq_domain hierarchy design, so I can prepare some patch or share my code to help others. Best regards, Alexander
