Re: [Xen-devel] [PATCH v2 11/16] xen/arm: IRQ: Protect IRQ to be shared between domains and XEN

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2014-04-03 at 21:42 +0100, Julien Grall wrote:

$subject "do not allow IRQs to be shared between..."

> The current dt_route_irq_to_guest implementation set IRQ_GUEST no matter if 
> the

s/set/sets/; s/no matter if/even if/

> IRQ is correctly setup.

"is already correctly setup" (I think that's what you meant)

> As IRQ can be shared between devices, if the devices are not assigned to the

s/As/An/ ?

> same domain or Xen, this could result to route the IRQ to the domain instead 
> of

"then this could result in routing the IRQ..."

> Xen ...
> 
> Also avoid to rely on wrong behaviour when Xen is routing an IRQ to DOM0.

"Also avoid relying on the wrong behaviour ..." perhaps? If that not
then I'm not sure what this is referring to. Apart from that doubt the
code looks ok to me.

> 
> Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> 
> ---
>     Changes in v2:
>         - Use EBUSY instead of EADDRINUSE for error code
>         - Don't hardcode the domain in error message
>         - Fix typo in error message
>         - Use irq_get_domain
> ---
>  xen/arch/arm/domain_build.c |    9 +++++++--
>  xen/arch/arm/irq.c          |   34 +++++++++++++++++++++++++++++++++-
>  2 files changed, 40 insertions(+), 3 deletions(-)
> 
> diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
> index e7b1674..f85e5a9 100644
> --- a/xen/arch/arm/domain_build.c
> +++ b/xen/arch/arm/domain_build.c
> @@ -718,8 +718,13 @@ static int map_device(struct domain *d, const struct 
> dt_device_node *dev)
>          }
>  
>          DPRINT("irq %u = %u type = 0x%x\n", i, irq.irq, irq.type);
> -        /* Don't check return because the IRQ can be use by multiple device 
> */
> -        route_dt_irq_to_guest(d, &irq, dt_node_name(dev));
> +        res = route_dt_irq_to_guest(d, &irq, dt_node_name(dev));
> +        if ( res )
> +        {
> +            printk(XENLOG_ERR "Unable to route IRQ %u to domain %u\n",
> +                   irq.irq, d->domain_id);
> +            return res;
> +        }
>      }
>  
>      /* Map the address ranges */
> diff --git a/xen/arch/arm/irq.c b/xen/arch/arm/irq.c
> index 1262a9c..2bf6618 100644
> --- a/xen/arch/arm/irq.c
> +++ b/xen/arch/arm/irq.c
> @@ -253,6 +253,16 @@ int setup_dt_irq(const struct dt_irq *irq, struct 
> irqaction *new)
>  
>      spin_lock_irqsave(&desc->lock, flags);
>  
> +    if ( desc->status & IRQ_GUEST )
> +    {
> +        struct domain *d = irq_get_domain(desc);
> +
> +        spin_unlock_irqrestore(&desc->lock, flags);
> +        printk(XENLOG_ERR "ERROR: IRQ %u is already in use by the domain 
> %u\n",
> +               irq->irq, d->domain_id);
> +        return -EBUSY;
> +    }
> +
>      disabled = (desc->action == NULL);
>  
>      rc = __setup_irq(desc, new);
> @@ -289,7 +299,7 @@ int route_dt_irq_to_guest(struct domain *d, const struct 
> dt_irq *irq,
>      struct irqaction *action;
>      struct irq_desc *desc = irq_to_desc(irq->irq);
>      unsigned long flags;
> -    int retval;
> +    int retval = 0;
>      bool_t level;
>  
>      action = xmalloc(struct irqaction);
> @@ -302,6 +312,28 @@ int route_dt_irq_to_guest(struct domain *d, const struct 
> dt_irq *irq,
>  
>      spin_lock_irqsave(&desc->lock, flags);
>  
> +    /* If the IRQ is already used by someone
> +     *  - If it's the same domain -> Xen doesn't need to update the IRQ desc
> +     *  - Otherwise -> For now, don't allow the IRQ to be shared between
> +     *  Xen and domains.
> +     */
> +    if ( desc->action != NULL )
> +    {
> +        struct domain *ad = irq_get_domain(desc);
> +
> +        if ( (desc->status & IRQ_GUEST) && d == ad )
> +            goto out;
> +
> +        if ( desc->status & IRQ_GUEST )
> +            printk(XENLOG_ERR "ERROR: IRQ %u is already used by domain %u\n",
> +                   irq->irq, ad->domain_id);
> +        else
> +            printk(XENLOG_ERR "ERROR: IRQ %u is already used by Xen\n",
> +                   irq->irq);
> +        retval = -EBUSY;
> +        goto out;
> +    }
> +
>      retval = __setup_irq(desc, action);
>      if ( retval )
>      {



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