Re: [PATCH] x86/pass-through: avoid double IRQ unbind during domain cleanup

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Tue, Apr 28, 2020 at 02:21:48PM +0200, Jan Beulich wrote:
> XEN_DOMCTL_destroydomain creates a continuation if domain_kill -ERESTARTs.
> In that scenario, it is possible to receive multiple _pirq_guest_unbind
> calls for the same pirq from domain_kill, if the pirq has not yet been
> removed from the domain's pirq_tree, as:
>   domain_kill()
>     -> domain_relinquish_resources()
>       -> pci_release_devices()
>         -> pci_clean_dpci_irq()
>           -> pirq_guest_unbind()
>             -> __pirq_guest_unbind()
> 
> Avoid recurring invocations of pirq_guest_unbind() by removing the pIRQ
> from the tree being iterated after the first call there. In case such a
> removed entry still has a softirq outstanding, record it and re-check
> upon re-invocation.
> 
> Reported-by: Varad Gautam <vrd@xxxxxxxxx>
> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> Tested-by: Varad Gautam <vrd@xxxxxxxxx>
> 
> --- a/xen/arch/x86/irq.c
> +++ b/xen/arch/x86/irq.c
> @@ -1323,7 +1323,7 @@ void (pirq_cleanup_check)(struct pirq *p
>      }
>  
>      if ( radix_tree_delete(&d->pirq_tree, pirq->pirq) != pirq )
> -        BUG();
> +        BUG_ON(!d->is_dying);

I think to keep the previous behavior this should be:

BUG_ON(!is_hvm_domain(d) || !d->is_dying);

Since the pirqs will only be removed elsewhere if the domain is HVM?

Thanks, Roger.