Re: [Xen-devel] Question, How to share interrupt between Doms

[Peng Fan <peng.fan@xxxxxxx>]

> -----Original Message-----
> From: Julien Grall [mailto:julien.grall@xxxxxxx]
> Sent: 2018年10月3日 0:03
> To: Peng Fan <peng.fan@xxxxxxx>; Stefano Stabellini <sstabellini@xxxxxxxxxx>
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx; Andre Przywara
> <andre.przywara@xxxxxxx>
> Subject: Re: Question, How to share interrupt between Doms
> 
> On 02/10/2018 09:32, Peng Fan wrote:
> > Hi Julien, Stefano,
> 
> Hi Peng,
> 
> >
> > Do you have any suggestions on how to share one interrupt between Doms?
> 
> Sharing interrupts are usually a pain. You would need to forward the 
> interrupts
> to all the domains using that interrupt and wait for them to EOI. This has
> security implications because you don't want DomA to prevent DomB receiving
> another interrupt because the previous one has not been EOIed correctly.
> 
> > The issue is that a gpio controller has 32 in/out port, however it only has 
> > one
> binded interrupt. The interrupt handler needs to check the status bits to 
> check
> which port has interrupt coming.
> > In my case, there are different devices using gpio interrupt that needs to 
> > be
> assigned to different doms.
> 
>  From what you wrote, it looks like you expect the GPIO controller to be 
> shared
> with multiple domains.
> 
> I don't think it is safe to do that. You need one domain (or Xen) to fully 
> manage
> the controller. All the other domain will have to access either a virtual GPIO
> controller or PV one. In the former, interrupt would be virtual, while the 
> latter
> the interrupt would be through even channel.
> 
> So sharing interrupt should not be necessary. Did I miss anything?

When interrupts comes, the dom0 will handle that. Then forward the interrupt to 
domu.
But I did not find a good method to forward the interrupt and hook the 
interrupt in domu dts and domu driver.

In Domu, driver needs use request irq and the dts needs interrupt=<xx xx>. But  
when dom0 notify
remote, there is no hook in frontend driver and the other driver interrupt 
handler.

Thanks,
Peng.

> 
> Cheers,
> 
> --
> Julien Grall
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