Re: [PATCH v7 15/19] irqdomain: irq_domain_check_msi_remap

Marc Zyngier
2017-01-10T11:54:18Z

On 09/01/17 13:46, Eric Auger wrote:
> This new function checks whether all MSI irq domains
> implement IRQ remapping. This is useful to understand
> whether VFIO passthrough is safe with respect to interrupts.
>
> On ARM typically an MSI controller can sit downstream
> to the IOMMU without preventing VFIO passthrough.
> As such any assigned device can write into the MSI doorbell.
> In case the MSI controller implements IRQ remapping, assigned
> devices will not be able to trigger interrupts towards the
> host. On the contrary, the assignment must be emphasized as
> unsafe with respect to interrupts.
>
> Signed-off-by: Eric Auger <eric.auger@redhat.com>
>
> ---
> v5 -> v6:
> - use irq_domain_hierarchical_is_msi_remap()
> - comment rewording
>
> v4 -> v5:
> - Handle DOMAIN_BUS_FSL_MC_MSI domains
> - Check parents
> ---
> include/linux/irqdomain.h | 1 +
> kernel/irq/irqdomain.c | 23 +++++++++++++++++++++++
> 2 files changed, 24 insertions(+)
>
> diff --git a/include/linux/irqdomain.h b/include/linux/irqdomain.h
> index bc2f571..188eced 100644
> --- a/include/linux/irqdomain.h
> +++ b/include/linux/irqdomain.h
> @@ -222,6 +222,7 @@ struct irq_domain *irq_domain_add_legacy(struct device_node *of_node,
> void *host_data);
> extern struct irq_domain *irq_find_matching_fwspec(struct irq_fwspec *fwspec,
> enum irq_domain_bus_token bus_token);
> +extern bool irq_domain_check_msi_remap(void);
> extern void irq_set_default_host(struct irq_domain *host);
> extern int irq_domain_alloc_descs(int virq, unsigned int nr_irqs,
> irq_hw_number_t hwirq, int node,
> diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
> index 101ee8f..fff30cb 100644
> --- a/kernel/irq/irqdomain.c
> +++ b/kernel/irq/irqdomain.c
> @@ -278,6 +278,29 @@ struct irq_domain *irq_find_matching_fwspec(struct irq_fwspec *fwspec,
> EXPORT_SYMBOL_GPL(irq_find_matching_fwspec);
>
> /**
> + * irq_domain_check_msi_remap - Check whether all MSI
> + * irq domains implement IRQ remapping
> + */
> +bool irq_domain_check_msi_remap(void)
> +{
> + struct irq_domain *h;
> + bool ret = true;
> +
> + mutex_lock(&irq_domain_mutex);
> + list_for_each_entry(h, &irq_domain_list, link) {
> + if (irq_domain_is_msi(h) &&
> + !irq_domain_hierarchical_is_msi_remap(h)) {
> + ret = false;
> + goto out;

Let's avoid gotos if we can. a break statement will have the same effect
here, and we can drop the label.

> + }
> + }
> +out:
> + mutex_unlock(&irq_domain_mutex);
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(irq_domain_check_msi_remap);
> +
> +/**
> * irq_set_default_host() - Set a "default" irq domain
> * @domain: default domain pointer
> *
>

Thanks,

M.
--
Jazz is not dead. It just smells funny...