Re: [PATCH v2 17/40] iommu/arm-smmu-v3: Link domains and devices

Auger Eric
2018-09-10T15:16:25Z

Hi Jean-Philippe,

On 05/11/2018 09:06 PM, Jean-Philippe Brucker wrote:
> When removing a mapping from a domain, we need to send an invalidation to
> all devices that might have stored it in their Address Translation Cache
> (ATC). In addition when updating the context descriptor of a live domain,
> we'll need to send invalidations for all devices attached to it.
>
> Maintain a list of devices in each domain, protected by a spinlock. It is
> updated every time we attach or detach devices to and from domains.
>
> It needs to be a spinlock because we'll invalidate ATC entries from
> within hardirq-safe contexts, but it may be possible to relax the read
> side with RCU later.
>
> Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker-5wv7dgnIgG8@public.gmane.org>
> ---
> drivers/iommu/arm-smmu-v3.c | 28 ++++++++++++++++++++++++++++
> 1 file changed, 28 insertions(+)
>
> diff --git a/drivers/iommu/arm-smmu-v3.c b/drivers/iommu/arm-smmu-v3.c
> index 1d647104bccc..c892f012fb43 100644
> --- a/drivers/iommu/arm-smmu-v3.c
> +++ b/drivers/iommu/arm-smmu-v3.c
> @@ -595,6 +595,11 @@ struct arm_smmu_device {
> struct arm_smmu_master_data {
> struct arm_smmu_device *smmu;
> struct arm_smmu_strtab_ent ste;
> +
> + struct arm_smmu_domain *domain;
> + struct list_head list; /* domain->devices */
> +
> + struct device *dev;
This field addition and associated assignment in arm_smmu_attach_dev()
is not really documented in the commit message.

> };
>
> /* SMMU private data for an IOMMU domain */
> @@ -618,6 +623,9 @@ struct arm_smmu_domain {
> };
>
> struct iommu_domain domain;
> +
> + struct list_head devices;
> + spinlock_t devices_lock;
> };
>
> struct arm_smmu_option_prop {
> @@ -1470,6 +1478,9 @@ static struct iommu_domain *arm_smmu_domain_alloc(unsigned type)
> }
>
> mutex_init(&smmu_domain->init_mutex);
> + INIT_LIST_HEAD(&smmu_domain->devices);
> + spin_lock_init(&smmu_domain->devices_lock);
> +
> return &smmu_domain->domain;
> }
>
> @@ -1685,7 +1696,17 @@ static void arm_smmu_install_ste_for_dev(struct iommu_fwspec *fwspec)
>
> static void arm_smmu_detach_dev(struct device *dev)
> {
> + unsigned long flags;
> struct arm_smmu_master_data *master = dev->iommu_fwspec->iommu_priv;
> + struct arm_smmu_domain *smmu_domain = master->domain;
> +
> + if (smmu_domain) {
> + spin_lock_irqsave(&smmu_domain->devices_lock, flags);
> + list_del(&master->list);
> + spin_unlock_irqrestore(&smmu_domain->devices_lock, flags);
> +
> + master->domain = NULL;
> + }
>
> master->ste.assigned = false;
> arm_smmu_install_ste_for_dev(dev->iommu_fwspec);
> @@ -1694,6 +1715,7 @@ static void arm_smmu_detach_dev(struct device *dev)
> static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
> {
> int ret = 0;
> + unsigned long flags;
> struct arm_smmu_device *smmu;
> struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
> struct arm_smmu_master_data *master;
> @@ -1729,6 +1751,11 @@ static int arm_smmu_attach_dev(struct iommu_domain *domain, struct device *dev)
> }
>
> ste->assigned = true;
> + master->domain = smmu_domain;
> +
> + spin_lock_irqsave(&smmu_domain->devices_lock, flags);
> + list_add(&master->list, &smmu_domain->devices);
it is not totally obvious to me why master->domain = smmu_domain isn't
within the lock either for consistency. Same when deleting the node.

Thanks

Eric
> + spin_unlock_irqrestore(&smmu_domain->devices_lock, flags);
>
> if (smmu_domain->stage == ARM_SMMU_DOMAIN_BYPASS) {
> ste->s1_cfg = NULL;
> @@ -1847,6 +1874,7 @@ static int arm_smmu_add_device(struct device *dev)
> return -ENOMEM;
>
> master->smmu = smmu;
> + master->dev = dev;
> fwspec->iommu_priv = master;
> }
>
>