Re: [PATCH 1/1] irqdomain: Export __irq_domain_alloc_irqs() and irq_domain_free_irqs()

From: Alexander Popov
Date: Fri Jul 15 2016 - 21:32:01 EST

On 08.07.2016 11:34, Alexander Popov wrote:
> 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 ( ). 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?

Hello again, Thomas,

Did I properly answer your question? Will you accept my patch exporting these
two functions?

> 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.

Do you think my paravirtualization code registering a child irq_domain
for x86_vector_domain could bring any profit to the mainline?
I would be glad to put effort and do it.

Thanks again, sorry for disturbing.

Best regards,