Re: [Xen-devel] Possible bug on ARM with irq passthrough

[Julien Grall <julien.grall@xxxxxxx>]

Hi Ivan,

On 05/07/17 14:50, Ivan Pavic wrote:
> On 07/05/2017 02:55 PM, Julien Grall wrote:
> > Hi Ivan,
> >
> > On 05/07/17 13:36, Ivan Pavic wrote:
> > > On 07/05/2017 01:27 PM, Julien Grall wrote:
> > > > On 04/07/17 21:20, Ivan Pavić2 wrote:
> > > > > Hello,
> > > > Hi Ivan,
> > > >
> > > > > I'm testing IRQ latency on exynos5422. I'm using Xen 4.10-unstable. I
> > > > > used device passthrough for SPI irq 64. For guest domain I used
> > > > > FreeRTOS. When I use credit scheduler after destruction of domain,
> > > > > IRQ is released. I changed scheduler to credit2 and rtds at boot time
> > > > > and IRQ wasn't released after destruction. xl create
> > > > > dom-free-rtos.cfg fails with:
> > > > >
> > > > > libxl: error: libxl_create.c:1278:domcreate_launch_dm: Domain
> > > > > 5:failed give domain access to irq 64: Device or resource busy
> > > > >
> > > > > This is very strange because it doesn't happen with credit scheduler.
> > > > > This is output of xl dmesg:
> > > > >
> > > > > (XEN) IRQ 64 is already used by domain 1
> > > > >
> > > > > Everything works first time but when I destroy domain and try to
> > > > > create again it fails. It works normally with credit scheduler. In
> > > > > dom-free-rtos.cfg:
> > > > > ...
> > > > > irqs = [64]
> > > > > ....
> > > > The Domain 1 still seems to be alive, you can confirm by via "xl
> > > > list". You said it works with credit but not credit2. I think you hit
> > > > the bug described in [1].
> > > I checked xl-list. There is no domain with id 1, only dom0. Also I tried
> > > xenctx 1 which resulted in
> > >     xc_domain_getinfo: No such process
> > >
> > > Same problem is with rtds scheduler. As I said, no problem with credit
> > > scheduler.
> > IRQs assigned to a domain will be released by domain_vgic_free() when
> > calling release_guest_irq(). This is called by Xen when the domain is
> > fully destroyed.
> >
> > It might be possible the domain is waiting to be fully destroyed, and
> > therefore hidden from the toolstack. Can you check if the domain is
> > been destroyed by Xen. You can add printk in domain_destroy and
> > complete_domain_destroy.
> >
> >  * domain_destroy is called when there is no more reference on the
> > domain (see put_domain)
> >  * complete_domain_destroy is called when RCU is quiescent
> >
> > If you got a message in the former, but not the latter. Then you hit
> > the bug described in my previous e-mail.
>     Yes, I've got message only in domain_destroy.
Ok, so you are hitting the bug described in my previous e-mail. I would 
recommend to stick on credit1 until this bug is fixed (I will mark it as 
a blocker).
Cheers,

--
Julien Grall

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