linux-kernel - Re: [PATCH v7 15/19] irqdomain: irq_domain_check_msi

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Message-ID: <810b8c1d-ec2a-bef0-c771-e93d59d6c5be@arm.com>
Date:   Tue, 10 Jan 2017 11:54:12 +0000
From:   Marc Zyngier <marc.zyngier@....com>
To:     Eric Auger <eric.auger@...hat.com>, eric.auger.pro@...il.com,
        christoffer.dall@...aro.org, robin.murphy@....com,
        alex.williamson@...hat.com, will.deacon@....com, joro@...tes.org,
        tglx@...utronix.de, jason@...edaemon.net,
        linux-arm-kernel@...ts.infradead.org
Cc:     kvm@...r.kernel.org, drjones@...hat.com,
        linux-kernel@...r.kernel.org, pranav.sawargaonkar@...il.com,
        iommu@...ts.linux-foundation.org, punit.agrawal@....com,
        diana.craciun@....com, gpkulkarni@...il.com,
        shankerd@...eaurora.org, bharat.bhushan@....com,
        geethasowjanya.akula@...il.com
Subject: Re: [PATCH v7 15/19] irqdomain: irq_domain_check_msi_remap

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@...hat.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...