[PATCH v2 5/8] iommu/arm-smmu-v3: Report IOMMU_CAP_ENFORCE_CACHE_COHERENCY for CANWBS

Jason Gunthorpe
2024-08-27T15:59:23Z

HW with CANWBS is always cache coherent and ignores PCI No Snoop requests
as well. This meets the requirement for IOMMU_CAP_ENFORCE_CACHE_COHERENCY,
so let's return it.

Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
---
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c | 35 +++++++++++++++++++++
drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h | 1 +
2 files changed, 36 insertions(+)

diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
index e2b97ad6d74b03..c2021e821e5cb6 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.c
@@ -2253,6 +2253,9 @@ static bool arm_smmu_capable(struct device *dev, enum iommu_cap cap)
case IOMMU_CAP_CACHE_COHERENCY:
/* Assume that a coherent TCU implies coherent TBUs */
return master->smmu->features & ARM_SMMU_FEAT_COHERENCY;
+ case IOMMU_CAP_ENFORCE_CACHE_COHERENCY:
+ return dev_iommu_fwspec_get(dev)->flags &
+ IOMMU_FWSPEC_PCI_RC_CANWBS;
case IOMMU_CAP_NOEXEC:
case IOMMU_CAP_DEFERRED_FLUSH:
return true;
@@ -2263,6 +2266,28 @@ static bool arm_smmu_capable(struct device *dev, enum iommu_cap cap)
}
}

+static bool arm_smmu_enforce_cache_coherency(struct iommu_domain *domain)
+{
+ struct arm_smmu_domain *smmu_domain = to_smmu_domain(domain);
+ struct arm_smmu_master_domain *master_domain;
+ unsigned long flags;
+ bool ret = false;
+
+ spin_lock_irqsave(&smmu_domain->devices_lock, flags);
+ list_for_each_entry(master_domain, &smmu_domain->devices,
+ devices_elm) {
+ if (!(dev_iommu_fwspec_get(master_domain->master->dev)->flags &
+ IOMMU_FWSPEC_PCI_RC_CANWBS))
+ goto out;
+ }
+
+ smmu_domain->enforce_cache_coherency = true;
+ ret = true;
+out:
+ spin_unlock_irqrestore(&smmu_domain->devices_lock, flags);
+ return ret;
+}
+
struct arm_smmu_domain *arm_smmu_domain_alloc(void)
{
struct arm_smmu_domain *smmu_domain;
@@ -2693,6 +2718,15 @@ static int arm_smmu_attach_prepare(struct arm_smmu_attach_state *state,
* one of them.
*/
spin_lock_irqsave(&smmu_domain->devices_lock, flags);
+ if (smmu_domain->enforce_cache_coherency &&
+ !(dev_iommu_fwspec_get(master->dev)->flags &
+ IOMMU_FWSPEC_PCI_RC_CANWBS)) {
+ kfree(master_domain);
+ spin_unlock_irqrestore(&smmu_domain->devices_lock,
+ flags);
+ return -EINVAL;
+ }
+
if (state->ats_enabled)
atomic_inc(&smmu_domain->nr_ats_masters);
list_add(&master_domain->devices_elm, &smmu_domain->devices);
@@ -3450,6 +3484,7 @@ static struct iommu_ops arm_smmu_ops = {
.owner = THIS_MODULE,
.default_domain_ops = &(const struct iommu_domain_ops) {
.attach_dev = arm_smmu_attach_dev,
+ .enforce_cache_coherency = arm_smmu_enforce_cache_coherency,
.set_dev_pasid = arm_smmu_s1_set_dev_pasid,
.map_pages = arm_smmu_map_pages,
.unmap_pages = arm_smmu_unmap_pages,
diff --git a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
index 7e8d2f36faebf3..45882f65bfcad0 100644
--- a/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
+++ b/drivers/iommu/arm/arm-smmu-v3/arm-smmu-v3.h
@@ -787,6 +787,7 @@ struct arm_smmu_domain {
/* List of struct arm_smmu_master_domain */
struct list_head devices;
spinlock_t devices_lock;
+ bool enforce_cache_coherency : 1;

struct mmu_notifier mmu_notifier;
};
--
2.46.0